This suit in the 4T size fits my very small 5 1/2 year old.  Torso feels slightly short, but still pretty good.  Not quite as snug throughout the body as he needs, but he's very slim, not a gram of fat on him.  He is 36.5 pounds, 42.5 inches tall (about the size of an average 4 year old).  He gets very cold during swim lessons, even in an indoor pool, and just won't swim in a regular bathing suit, he insists on a zip up suit.  I like the quality of the neoprene, and that it is neoprene through the whole leg.  Only the sleeves/shoulders are nylon/spandex blend.  The neoprene always holds up well to daily swimming, but the nylon/spandex blend areas (usually sleeves/shoulders/legs or portions of the legs) always stretch and wear out first.  Eventually those areas bag and sag past the elbows and knees and hinder his swimming movements.  Sleeves are little shorter which may help in that area.  Legs are also a touch on the shorter side.  Overall I'm pleased, the suit keeps him comfortable in an out of the pool, and he prefers the front zip.  I just wish they sold these suits in a "slim" size, because one size really does not fit all body types and the neoprene doesn't lend itself to stretching for fit, so they seem to cut them a little generous to prevent it being too snug or restrictive.  For warmth the suit should fit snuggly, just not tight.  As slim as my little guy is, we will never get that "snug" fit that would be ideal.

My tiny daughter can now finish her swim lessons in warmth and comfort

my son wear this suit for swimming class.

Wish this product had more spandex.  Even though the size is good in length, on a tiny frame it is baggy.  I am having my daughter wear a suit underneath it as well.  It is doing its job keeping her warm during swim practice.

Awsome! This thermal suit works very well. My 7-year-old likes it a lot. It keeps her worm.

This is my son's first thermal suit and seems very comfy.  The sizing seems just right.