These are a bit tricky to adjust as far as keeping the shoulder straps tight, but I taught at a climbing wall this past summer and got it to fit kids from 4 to about 9, so if you have a fast-growing little one or several that you want to trade it between, this would definitely be a good choice.

Fits even my 3-yr old Daughter. Very little danger of slipping out even at her 37" height. As a safety harness it is great. Wouldn't want to hang from it for an hour though -- no padding.

I bought the Simba and this harness for my sons to hike on trails and boulder in yosemite. I bought the simba at the REI store for my 3 year old (45", 40 lbs) and prayed that this one would fit my 1.5 year old (34" height, 26lbs) once we got it in the mail. It did. He loved the harness. The back cross over is movable so unlike the Simba I could get the torso short enough for my 1.5 year old. I actually hooked the front 2 loops together with a caribiner and then put another one in the back (over the crossed straps and waist strap) to hold the leash strap. I used this as a lead harness this way my son would walk/run in front of me and I could keep him from falling down the trails. I could then also hold it taut while he walked over rocks in the water and up boulders. We would also have him run and then jump and we would pick him up and he could start flying. Both my kids loved using the harnesses since they then were confident that they could climb and run anywhere with mom and dad close by and keeping them from falling. Since I had to basically make it the smallest possible I had a lot of extra strap that I had to tie up to keep my son from tripping. With all the extra straps and arm/leg holes things would get twisted and take a few seconds to figure out how to get back into the harness. The harness legs would also start pulling up loose shorts with all the running around we were doing. The shoulder straps would also start to fall off but then I would start tightening them again.