1911 Mag-well Mainspring Housing, Fusion Firearms, 1911 Serrated Mainspring Housing Mag-Well in Aluminum, Silver Finish. These are Top Quality Professional Series Parts; Made from the best materials and processes available in today's market. 2 piece Dovetail base well with set screw. This is a UMG Plain mainspring housing. All Machined from 6061 Aluminum and great looking and feeling serrated back pattern. These are as nice as they get. Will work for full size and commander size 1911 pistols.