The M4A4 | Mainframe is a Industrial Grade rifle skin from The 2018 Nuke Collection, distributed through the London 2018 Nuke Souvenir Package.

The float range for this finish is restricted to 0.00–0.50, so Factory New, Minimal Wear, Field-Tested, Well-Worn, and Battle-Scarred are the only obtainable conditions on the open market. The restricted range is set by Valve at the time of release.

A Souvenir version is available, dropped exclusively from cases collected during Major Championship matches and stamped with that tournament's stickers. Active listings for M4A4 | Mainframe are tracked across 18 marketplaces, with prices spanning $0.02 to $12.30 depending on wear, variant, and seller.