The pressure slide/pressure die is designed to force the tube onto the profile of the former. Generally the pressure slide is allowed free linear movement to travel with the tube during bending. Pressure dies may be static, depending on the materials and bend CLR. To bend thin wall tubes, typically to aerospace specifications and as a general design feature, a power follower slide may be fitted to the machine to provide hydraulic assistance to the linear travel of the pressure die. This should be adjustable in pressure and feed-rate and will help considerably to overcome drag, which on materials such as aluminium will result in excessive wall thinning. Clamp slippage may also be a result of drag.