okay this morning i tried it off of the first story part of my school, which is about 15feet...it was still Dewey outside so i slid a little but it did slow me down enough to not have to roll...only problem with this is the shoes and trying to get the right distance away from the wall...the shoes are kinda thrashed now, and if you get to far away from the wall its useless and if you are to close you want to hold your hands against the wall which is a really bad idea..but it your just touch the wall as you slide down to help stabilize your self it really helps
NOTE: you should always roll out of a drop to not put to much pressure on your back and legs, i did not roll to see if it actually slowed me down enough to help