I have two that I've used on Schwinns so far. One I bought for $7 at a shop and it looks like a splined socket. The other style I encountered looked like it needed a huge screwdriver as it had slots. I made a remover for that one with a piece of stainless steel and an angle grinder. Slap it in a vice, put the wheel down on it and spin the freewheel right off!