I bought this for my son (just turned 8, 49", 48 lbs) in a size 6. It is large, but he can still wear it. The photo is a size 6 hyperflex laying on top of an O'Neill size 10 (the shoulders are matched up). The O'Neill fit is good for a skinny kid. The Hyperflex is the same width in some spots, including the thighs and may be a better choice for a thicker kid. The Hyperflex material feels thinner than the 2mm O'Neill. For my thin child, I'd rather spend the same amount on a used size 6 O'Neill wetsuit for a better fit.

Reminds our preschooler son of when he tried out surfing w his big teenage cousins.
We've now had 2 of these size 4 and 6.

Sizing: Our son has outgrown each of his suits well before he hits manufacturers recommended sizing. He's a tall 5y.o (going on 6) and he's already pushing out of the Size 6. He is 4' but has a long torso. We'll get him a size 8 unless we can someone who makes a 3mm half suit for kids at a reasonable price.
Durability: Very solid. He gets plenty of use as we live in the tropics. He's used it numerous times for surfing. Still looks great, no fraying.

Warmth: These definitely keep him warmer than this AquaSphere one-piece suit or his trunks plus long sleeve rash guard, but he still gets a little blue on the lips after 45min in a cool pool. But is fine chilly ocean water in the mid 70s.

The size 6 kids fit more like a size small 4. It was very small. I would definitely suggest a size bigger than you think you need. I had to send it back and order the next size up which was a size 8 for a average height. lean 5 year old. Otherwise, it seemed sturdy and well constructed. Nice looking, but couldn't try it on due to it being so small.

UPDATE: Got the size 8 and sure enough, it fit my 5 year old perfect. It was a little big in places, however, it is a really nice buy for the money. Great product so far.

We purchased this item in hopes that it would keep our child warm. In really cold water (i.e.,
Our child is 54inches and weighs about 55lbs; we purchased the size 6. It fits well, but since she is so skinny; their is 'extra' fabric around the mid-section. Nevertheless, a complete seal is formed on the legs. The neck area does not allow a complete seal, although there is an 'adjustable' flap that connects via velcro. Sometimes, excess water gets trapped at the legs (entering from the neck and getting trapped at thigh via the seal formed). Not too much of an issue and easily solved by breaking the seal and letting the water out. It is important to note that when the water does come out...it comes out warm...which means that the wet suit is doing its job!

The arm/shoulder area is made of a flexible material allowing full arm movement (although sacrificing some warmth due to the lack of neoprene). Our child is able to run/jump/swim easily in this suit. We have used it in both chlorinated pool water and salt water ocean. I was afraid that she would get too hot at the beach; but she never complained. The suit gives minimal buoyancy...not like an adult full size wetsuit. Construction seems good; although it is way too early to give a definitive opinion. Design-wise it is nice; makes your kid look like a mini-surfer.

Overall, for the $40-50 price point, this product is worth trying if you are looking for a flexible wetsuit to keep your child warm in moderately cool water (e.g., 70-80F).

My son gets very cold during his swim lessons (partially from his medication) and he wasn't able to focus as well because he wanted to get out of the pool and get warm. I purchased the wetsuit to help insulate his body and keep him warmer while swimming. I pair it with a long sleeved rash guard (worn under the suit) during his lessons to help maximize the warmth.

My husband explained to me that wetsuits work by circulating the water closer to your body, thus making the water stay warmer from your body temperature. I let my son get in the hot tub before his lessons start so his body temperature is higher and this combination has worked very well as a result.

My son is very slender and I purchased this wet suit for him with the intention of him being able to grow into a little. I purchased a size 8 (he wears a 7 Slim in Children's Place clothing as a reference), so I knew the wet suit would be a little large circumference wise. As I hoped, the length was correct while the width was a bit large. He should be able to grow in this suit for a while.

The wet suit itself is made of a very nice, thick (3 mm) material. It's very high quality (great stitching, good attention to detail, no loose pieces). I think it was a great value.