Lifetime Wave™ Kayak - The 6 ft. youth Wave™ Kayak has a 130 lb. weight capacity and comes in yellow. One double-sided paddle is included. 5-year limited warranty. The 6 ft. Lifetime Wave™ Kayak is specifically designed for kids ages 5 and up, or up to 130 lbs. The wide stance provides a stable paddling platform to keep your child safely in the kayak. It’s sloped back end and swim-up step allows the rider to easily re-enter the kayak from the water. With scupper holes, multiple footrest positions, and great stability, the Wave™ is perfect for kids recreational kayaking.

Ergonomic cockpit design enhances balance and motor skills

Molded finger handles on each side of the youth kayak

Reverse chine for enhanced stability with swim-up step

Lightweight 18 lb. Design - 130 lb. Weight capacity

Recommended for ages 5 and up with Adult supervision - Paddle included

Does this kayak come with the seat back in the picture?
Yes; it's a soft fabric-like sling back seat and it did come with it.

where can I find just the seat for this kayak? my son has this one but it did not come with a seat and he cant go on long floats without one
I had to order my son’s off amazon. It was the “Lixada ​1pc Adjustable Kayaking Canoeing Sit On Top Kayak Seat Back Rest Seat Backrest Support Back Pad Band Antiskid Cushiony Black” and cost $21.99

What is the Sh size?
Scupper hole size is about 1” to 1 1/8” in diameter.

how stable is this kayak? is it easy/hard to tip over?
Very stable. My nine year old girl can zip around the wavy Lake Michigan. Even I can use it for fun close to the shore(117lbs).