Down in my barns outdoor arena there are a few jump standards, one of them is the plastic(maybe fiberglass)standard a keyhole track and jump cups and there are measurements on some of the holes. My friend was jumping my TB and wanted me to raise the jump so going on measurements I figured 2'6 would be a good height. She has comfortably jumped a little over 2' before so I figured that would be a comfortable height but after I stepped back and looked at the jump I set up it seemed much higher. She hesitantly jumped it anyway(I told her I would lower it if she didn't feel ready) and thoroughly enjoyed the thrill lol. When I got home and was telling my husband about the jump and showed him about how high it was he thought it seemed higher then 2'6, so I got a tape measure and agreed it seemed more like 3' so I told her she should measure and sure enough it measured 3'4! So the whole point of the ramble is why would the standard read 2'6 when it was 3'4! That is a HUGH difference!