Nighthawk Custom Mainspring Housing Drop-In Government 25 LPI Checkering Blued Carbon No Well Cut Fully Machined Steel. Each mainspring housing is Fully Machined from a solid steel and blued to provide unmatched durability. To improve grip on the pistol 25 LPI checkering has been added. Experience the Nighthawk Difference with the highest quality drop-in parts available. Specifications for Nighthawk Custom Drop-In Mainspring Housing: Manufacturer: Nighthawk Custom Gun Make: 1911 Platform Gun Model: 1911 Package Contents: Nighthawk Custom Drop-In Mainspring Housing What firearm models does the manufacturer say Nighthawk Custom Drop-In Mainspring Housing is compatible with? The manufacturer suggests that Nighthawk Custom Drop-In Mainspring Housing is compatible with 1911Nighthawk Custom SDP1040: Mainspring Housing Drop-In Government 25 LPI Checkering Blued Carbon No Well Cut Fully Machined Steel