My son typically wears a size 5 so I purchased ...
929817
My son typically wears a size 5 so I purchased a size 6 to get a little more wear out of it.  They fit perfectly now.  I only gave this 4 stars because of the fit but otherwise he loves them!
4340632
Too small despite labeled as the correct size for my son (size 4). My son wears a size 3. I returned and ordered a larger size (size 5) from the same seller. Now the new Heelys is a bit loose, but not enough to stop my kid from skating around.
4850038
My son wears a size 3 .. don't think these would cover much bigger than that .
2748709
The sizing info online said that the size 5/6 is for 42.5-49" tall and 42.5-53lbs.  Sounded perfect for my 5yo (about 47" and 50lb when I ordered the pants).  I received the item and the tag hanging from it said 42.5-45" tall and 42.5-48lb.  I freaked out.  My guy is out of both of those specs!  The pants fit ok, however.  They were a bit short, but not too bad.  After playing in the snow in the morning for a couple hours, there was leakage in the seat bottom requiring a change of clothing.  The snow pants dried out fairly quickly, however, and were good to go for more snow play in the afternoon.  My son never complained about the pants.
4515589
My son is 5 years old, and this fit perfectly.  He normally wears a size 6-7 and is 51 pounds.  It may be a little snug by the time that he's closer to 90 pounds, I'm not sure that it would last that long.
2660609
My son liked the socks but they were a little big doe his size 10.5 shoe size
2449277
Some reviews advised buying a size down and i did but it turned out to be somewhat small for my son, would advise buying your kids normal size.
3380976
somewhat small for my 3.5 yrs old son. I had to return
3468296
The normal Crocs Size 11/12 is too big for my 5 year old.  I love that this style has size 11, not size 11/12, and it fits just right with a little room to grow.  My boy loves it.  And it's $10 cheaper than Crocs site.  I'm happy.
4280219
I bought a size 5 for my son & it was super tiny. It wasn't much bigger than a Childrens Place 3T for my other son. Material was good quality though.
2671184
My son just turn 4 got him a size 5 finish him a little loose but its ok because  I rather it to be  a little big than too small..
2287835
My son lives the shoe. I purchased a size up based on previous reviewa. Several light settings. He's 5 and wore to school still works fine.
1822138
I order this sneaker because my son liked it, I ordered size 5 for big kids, when my purchase arrived it was size 5 but for toddler , my son got upset and I have to return it , now I don't know if I order again my son still likes those sneakers
2747623
My son wear it all the time it's a little bit small . His 5 years old and very skinny little boy
3093713
I wear size 7, so it was expected they'd be on the larger size
4094433
My son is very tall for his age so I always buy a 5 even though it's a little big for him. The suit fit well, not really big at all. If anything the legs were shorter than typical 5's. It looks nice though and is a decent suit for the price.
1877807
I bought a size 5 for my petite 6 year old--she wears size 5 in regular clothes.  It is super-cute and she loves it!