CNC Steel version of the variable mass piston body, for extreme mass configuration (55.1 grams instead of 19.0 grams for the aluminium version).   Compatible with:   – original SRS piston (SBA-BPS-13) – original TAC-41 piston (SBA-BPS-30) – variable mass piston for SRS (SBA-BPS-18) – variable mass piston for TAC-41 (SBA-BPS-31) – original SRS piston end (SBA-BPE-01) – original TAC-41 piston end (SBA-BPE-03)