The MAR-1 Trigger works in all pre-2004 Marlin bolt action rifles chambered in .22 LR, .22 WMR and .17 HMR. It is a 100% drop in trigger and will adjust from 1 lb. to 2 lbs.
The MAR-2 Trigger works for all post 2004 production 900 Series Marlin rifles.
Sinclair, Issue:4B, Page:255