Limiters are made to match the profile of the cutters they are to be paired with, and are made from a milder steel than the cutter. The limiters sit just behind the depth of the cutter, and limit the depth of cut in each pass, which minimises the chance of kickback.
A limiter does not reduce the depth of cut, so full profile cutting is possible, though the feed rate may need to be reduced accordingly.
It is highly recommended limiters are used when using spindle moulders.