There has been a design change in the older style AMP series rollers. The older AMP series roller shafts and rollers were steel and had brass bushings in the steel rollers.
The new AMP series roller shafts are stainless steel and the rollers are Delrin (a lightweight but durable low-wear, low-friction plastic). The Delrin rollers contain sealed ball bearings. This new design is very corrosion resistant and has better wear properties.
