Replacement blades for Supreme Duty QPC-501, Medium Duty QPC-502, and Premium QPC-506 are QPC-506B.

Replacement blades for Slim Line QPC-503 are QPC-503B.

Replacement blades for Box Cutter QPC-504 are QPC-504B.

Replacement blades for Heavy Duty QPC-505 are QPC-505B.