Arrow HK12BB 32D Cylindrical Storeroom Knob Lock, BB Knob Trim Design, in Satin Stainless Steel finish. The HK series Grade 1 Cylindrical Knob lock is designed and tested for the most robust applications for Grade 1 knob locksets. Backed by the Arrow 10 year warranty and Certified to BHMA Grade 1 it is the worry-free solution when a Grade 1 knob lock is needed.