Pewter ‘Mushroom’ Rim Knob (Unsprung) PF437 Rose – 2″ (52mm) Knob 2 1/8″ (55mm) This is designed specifically for a rim lock – you only receive one backplate. Pewter Patina over high quality brass casting. suitable for modern or period homes. This finish has excellent anti-corrosion properties. Care. a wipe over with a damp cloth is all that required ( maintenance free finish )