1/2"-20 Serrated Flange Lock Nut - Plated 1/2"-20 serrated flange lock nut - plated SFN1220 $0.306/ea
1/4"-28 Serrated Flange Lock Nut - Plated 1/4"-28 serrated flange lock nut - plated SFN1428 $0.060/ea