20691, 20701, 20481, 20461: No rust SS ball bearing; Chrome plated brass
20441, 20531, 20571, 20591, 20521, 20541, 20551, 20621, 20671, 20661: Acetal body with SS ball bearing and thumb lever
20601: Acetal body for dimension stability
20501, 20511, 20641, 20651: Brass construciton
UPC: 719249205618
Model Number: 20561