diff --git a/src/Cart.php b/src/Cart.php
index fc33359..8d69209 100644
--- a/src/Cart.php
+++ b/src/Cart.php
@@ -23,24 +23,20 @@ class Cart
 
     /**
      * Instance of the session manager.
-     *
-     * @var \Illuminate\Session\SessionManager
      */
-    private $session;
+    private \Illuminate\Session\SessionManager $session;
 
     /**
      * Instance of the event dispatcher.
-     *
-     * @var \Illuminate\Contracts\Events\Dispatcher
      */
-    private $events;
+    private \Illuminate\Contracts\Events\Dispatcher $events;
 
     /**
      * Holds the current cart instance.
      *
      * @var string
      */
-    private $instance;
+    private string $instance;
 
     /**
      * Holds the creation date of the cart.
@@ -92,7 +88,7 @@ class Cart
      *
      * @return \Gloudemans\Shoppingcart\Cart
      */
-    public function instance($instance = null)
+    public function instance(?string $instance = null)
     {
         $instance = $instance ?: self::DEFAULT_INSTANCE;
 
@@ -128,7 +124,7 @@ class Cart
      *
      * @return \Gloudemans\Shoppingcart\CartItem
      */
-    public function add($id, $name = null, $qty = null, $price = null, $weight = 0, array $options = [])
+    public function add($id, ?string $name = null, $qty = null, $price = null, $weight = 0, array $options = [])
     {
         if ($this->isMulti($id)) {
             return array_map(function ($item) {
@@ -151,7 +147,7 @@ class Cart
      *
      * @return \Gloudemans\Shoppingcart\CartItem The CartItem
      */
-    public function addCartItem($item, $keepDiscount = false, $keepTax = false, $dispatchEvent = true)
+    public function addCartItem(CartItem $item, bool $keepDiscount = false, bool $keepTax = false, bool $dispatchEvent = true)
     {
         if (!$keepDiscount) {
             $item->setDiscountRate($this->discount);
@@ -190,7 +186,7 @@ class Cart
      *
      * @return \Gloudemans\Shoppingcart\CartItem
      */
-    public function update($rowId, $qty)
+    public function update(string $rowId, $qty)
     {
         $cartItem = $this->get($rowId);
 
@@ -245,7 +241,7 @@ class Cart
      *
      * @return void
      */
-    public function remove($rowId)
+    public function remove(string $rowId)
     {
         $cartItem = $this->get($rowId);
 
@@ -267,7 +263,7 @@ class Cart
      *
      * @return \Gloudemans\Shoppingcart\CartItem
      */
-    public function get($rowId)
+    public function get(string $rowId)
     {
         $content = $this->getContent();
 
@@ -315,20 +311,16 @@ class Cart
     /**
      * Get the amount of CartItems in the Cart.
      * Keep in mind that this does NOT count quantity.
-     *
-     * @return int|float
      */
-    public function countItems()
+    public function countItems() : int
     {
         return $this->getContent()->count();
     }
 
     /**
      * Get the total price of the items in the cart.
-     *
-     * @return float
      */
-    public function totalFloat()
+    public function totalFloat() : float
     {
         return $this->getContent()->reduce(function ($total, CartItem $cartItem) {
             return $total + $cartItem->total;
@@ -337,24 +329,16 @@ class Cart
 
     /**
      * Get the total price of the items in the cart as formatted string.
-     *
-     * @param int    $decimals
-     * @param string $decimalPoint
-     * @param string $thousandSeperator
-     *
-     * @return string
      */
-    public function total($decimals = null, $decimalPoint = null, $thousandSeperator = null)
+    public function total(?int $decimals = null, ?string $decimalPoint = null, ?string $thousandSeperator = null) : string
     {
         return $this->numberFormat($this->totalFloat(), $decimals, $decimalPoint, $thousandSeperator);
     }
 
     /**
      * Get the total tax of the items in the cart.
-     *
-     * @return float
      */
-    public function taxFloat()
+    public function taxFloat() : float
     {
         return $this->getContent()->reduce(function ($tax, CartItem $cartItem) {
             return $tax + $cartItem->taxTotal;
@@ -363,24 +347,16 @@ class Cart
 
     /**
      * Get the total tax of the items in the cart as formatted string.
-     *
-     * @param int    $decimals
-     * @param string $decimalPoint
-     * @param string $thousandSeperator
-     *
-     * @return string
      */
-    public function tax($decimals = null, $decimalPoint = null, $thousandSeperator = null)
+    public function tax(?int $decimals = null, ?string $decimalPoint = null, ?string $thousandSeperator = null) : string
     {
         return $this->numberFormat($this->taxFloat(), $decimals, $decimalPoint, $thousandSeperator);
     }
 
     /**
      * Get the subtotal (total - tax) of the items in the cart.
-     *
-     * @return float
      */
-    public function subtotalFloat()
+    public function subtotalFloat() : float
     {
         return $this->getContent()->reduce(function ($subTotal, CartItem $cartItem) {
             return $subTotal + $cartItem->subtotal;
@@ -396,7 +372,7 @@ class Cart
      *
      * @return string
      */
-    public function subtotal($decimals = null, $decimalPoint = null, $thousandSeperator = null)
+    public function subtotal(?int $decimals = null, ?string $decimalPoint = null, ?string $thousandSeperator = null) : string
     {
         return $this->numberFormat($this->subtotalFloat(), $decimals, $decimalPoint, $thousandSeperator);
     }
@@ -406,7 +382,7 @@ class Cart
      *
      * @return float
      */
-    public function discountFloat()
+    public function discountFloat() : float
     {
         return $this->getContent()->reduce(function ($discount, CartItem $cartItem) {
             return $discount + $cartItem->discountTotal;
@@ -415,24 +391,16 @@ class Cart
 
     /**
      * Get the discount of the items in the cart as formatted string.
-     *
-     * @param int    $decimals
-     * @param string $decimalPoint
-     * @param string $thousandSeperator
-     *
-     * @return string
      */
-    public function discount($decimals = null, $decimalPoint = null, $thousandSeperator = null)
+    public function discount(?int $decimals = null, ?string $decimalPoint = null, ?string $thousandSeperator = null) : string
     {
         return $this->numberFormat($this->discountFloat(), $decimals, $decimalPoint, $thousandSeperator);
     }
 
     /**
      * Get the price of the items in the cart (not rounded).
-     *
-     * @return float
      */
-    public function initialFloat()
+    public function initialFloat() : float
     {
         return $this->getContent()->reduce(function ($initial, CartItem $cartItem) {
             return $initial + ($cartItem->qty * $cartItem->price);
@@ -441,24 +409,16 @@ class Cart
 
     /**
      * Get the price of the items in the cart as formatted string.
-     *
-     * @param int    $decimals
-     * @param string $decimalPoint
-     * @param string $thousandSeperator
-     *
-     * @return string
      */
-    public function initial($decimals = null, $decimalPoint = null, $thousandSeperator = null)
+    public function initial(?int $decimals = null, ?string $decimalPoint = null, ?string $thousandSeperator = null) : string
     {
         return $this->numberFormat($this->initialFloat(), $decimals, $decimalPoint, $thousandSeperator);
     }
 
     /**
      * Get the price of the items in the cart (previously rounded).
-     *
-     * @return float
      */
-    public function priceTotalFloat()
+    public function priceTotalFloat() : float
     {
         return $this->getContent()->reduce(function ($initial, CartItem $cartItem) {
             return $initial + $cartItem->priceTotal;
@@ -467,24 +427,16 @@ class Cart
 
     /**
      * Get the price of the items in the cart as formatted string.
-     *
-     * @param int    $decimals
-     * @param string $decimalPoint
-     * @param string $thousandSeperator
-     *
-     * @return string
      */
-    public function priceTotal($decimals = null, $decimalPoint = null, $thousandSeperator = null)
+    public function priceTotal(?int $decimals = null, ?string $decimalPoint = null, ?string $thousandSeperator = null) : string
     {
         return $this->numberFormat($this->priceTotalFloat(), $decimals, $decimalPoint, $thousandSeperator);
     }
 
     /**
      * Get the total weight of the items in the cart.
-     *
-     * @return float
      */
-    public function weightFloat()
+    public function weightFloat() : float
     {
         return $this->getContent()->reduce(function ($total, CartItem $cartItem) {
             return $total + ($cartItem->qty * $cartItem->weight);
@@ -500,7 +452,7 @@ class Cart
      *
      * @return string
      */
-    public function weight($decimals = null, $decimalPoint = null, $thousandSeperator = null)
+    public function weight(?int $decimals = null, ?string $decimalPoint = null, ?string $thousandSeperator = null) : string
     {
         return $this->numberFormat($this->weightFloat(), $decimals, $decimalPoint, $thousandSeperator);
     }
@@ -512,7 +464,7 @@ class Cart
      *
      * @return \Illuminate\Support\Collection
      */
-    public function search(Closure $search)
+    public function search(Closure $search) : Collection
     {
         return $this->getContent()->filter($search);
     }
@@ -525,7 +477,7 @@ class Cart
      *
      * @return void
      */
-    public function associate($rowId, $model)
+    public function associate(string $rowId, $model)
     {
         if (is_string($model) && !class_exists($model)) {
             throw new UnknownModelException("The supplied model {$model} does not exist.");
@@ -550,7 +502,7 @@ class Cart
      *
      * @return void
      */
-    public function setTax($rowId, $taxRate)
+    public function setTax(string $rowId, $taxRate)
     {
         $cartItem = $this->get($rowId);
 
@@ -589,7 +541,7 @@ class Cart
      *
      * @return void
      */
-    public function setDiscount($rowId, $discount)
+    public function setDiscount(string $rowId, $discount)
     {
         $cartItem = $this->get($rowId);
 
@@ -732,7 +684,7 @@ class Cart
      *
      * @return bool
      */
-    public function merge($identifier, $keepDiscount = false, $keepTax = false, $dispatchAdd = true, $instance = self::DEFAULT_INSTANCE)
+    public function merge($identifier, bool $keepDiscount = false, bool $keepTax = false, bool $dispatchAdd = true, $instance = self::DEFAULT_INSTANCE)
     {
         if (!$this->storedCartInstanceWithIdentifierExists($instance, $identifier)) {
             return false;
@@ -759,7 +711,7 @@ class Cart
      *
      * @return float|null
      */
-    public function __get($attribute)
+    public function __get(string $attribute)
     {
         switch ($attribute) {
             case 'total':
@@ -778,7 +730,7 @@ class Cart
      *
      * @return \Illuminate\Support\Collection
      */
-    protected function getContent()
+    protected function getContent() : Collection
     {
         if ($this->session->has($this->instance)) {
             return $this->session->get($this->instance);
@@ -799,7 +751,7 @@ class Cart
      *
      * @return \Gloudemans\Shoppingcart\CartItem
      */
-    private function createCartItem($id, $name, $qty, $price, $weight, array $options)
+    private function createCartItem($id, string $name, $qty, $price, $weight, array $options) : CartItem
     {
         if ($id instanceof Buyable) {
             $cartItem = CartItem::fromBuyable($id, $qty ?: []);
@@ -886,7 +838,7 @@ class Cart
      *
      * @return string
      */
-    private function numberFormat($value, $decimals, $decimalPoint, $thousandSeperator)
+    private function numberFormat($value, ?int $decimals = null, ?string $decimalPoint = null, ?string $thousandSeperator = null)
     {
         if (is_null($decimals)) {
             $decimals = config('cart.format.decimals', 2);
@@ -908,7 +860,7 @@ class Cart
      *
      * @return \Carbon\Carbon|null
      */
-    public function createdAt()
+    public function createdAt() : ?Carbon
     {
         return $this->createdAt;
     }
@@ -918,7 +870,7 @@ class Cart
      *
      * @return \Carbon\Carbon|null
      */
-    public function updatedAt()
+    public function updatedAt() : ?Carbon
     {
         return $this->updatedAt;
     }