Here are our ramps (1102). I've seen better, but we designed these to easily guide a robot up and ensure that they don't fall off.
Any size robot will fit as long as they don't exede the bumper regulations. We actually played with a team that did
but they simply removed the protruding bumper and climbed just fine.
If a robot is not all the way up yet we can raise the ramp part for a little extra help.
Linky, linky