For a precision spherical bearing, QA1's NPB-T Narrow Stainless Steel Series spherical bearings are the perfect selection. Each bearing is made from Stainless Steel with a PTFE liner and has tighter tolerances than traditional spherical bearings. Ball 440C Stainless Steel. Heat Treated. Hard Chrome Plated. Precision Ground. Liner PTFE Self-Lubricating. Race Stainless Steel. Heat Treated.