Schaefer Traveler systems are designed with real world loads in mind. Each track is extruded from thick-walled aluminium and is black hardcoat anodized for maximum corrosion resistance. In addition each track is treated with a Teflon(tm) impregnation to extend the life of the coating while reducing friction. Each traveler car contains separate "wheels" that hold "captive" stainless steel ball bearings. This captive wheel design with full radius races distributes bearing loads evenly to a greater surface contact area than other plastic bearing designs. They also allow you to remove the car for inspection without the loss of bearings. The control blocks use Schaefer's Delrin(tm) ball bearing sheaves and our Fast Entry Cam Cleats for ultimate control.