If it's out and out performance you want then a rectangular trampoline is probably the choice for you. Due to the shape the bounce in focused in the middle of the trampoline, usually where there is a cross or logo of manufacturer. Hit that spot consistantly and you'll be amazed what height you can get ! Rectangular trampolines do not give you the "bounce back to the middle" effect that round trampolines do so we believe enclosures are even more important. Unless of course you are a competing trampolinist then these are the closest you will get to a competition indoor trampoline, especially the z20 Extreme which even has a string bed.