Combination wipers are plastic wipers with an additional felt wiper (inside the ball nut). They are used where felt wipers are desirable, but need to be protected from water or water based fluids. Felt tends to absorb water, so it should not be used without the additional plastic wiper in such cases.
Special wipers which reliably remove coarse dirt particles (chips or similar) and prevent dusts from entering the nut are very recommended for application in machine tools. They ensure a consistent distribution of lubricant on the spindle thread while slightly increase the friction torque. Future designs will include a laser-sintered housing replacing the existing steel housing. Combination wipers can also be executed as a 2-part retrofit kit in special design.
Combination wipers add to the nut length - please consult Steinmeyer for details.