Evolution Gun Works Officer's Mainspring Housing 25 LPI 1911 Steel Blued Carbom Finish Blue. The checkering on this mainspring housing helps get the weight in the right place and gives you good traction.Pins and springs do not come with this part. You can use the pins and springs from your original mainspring housing or purchase new parts from us.This mainspring housing makes a great replacement for plastic mainspring housings.This is our premium mainspring housing designed and made by EGW. Fully machined from bar stock. This item will fit 1911 Officer's Model Frames. It is a flat mainspring housing. Specifications for Evolution Gun Works Officers Mainspring Housing 25 LPI: Manufacturer: Evolution Gun Works Fabric/Material: Steel Design/Pattern: Checkered Gun Make: 1911 Platform Gun Model: 1911 Condition: New Package Contents: Evolution Gun Works Officers Mainspring Housing 25 LPI What firearm models does the manufacturer say Evolution Gun Works Officers Mainspring Housing 25 LPI is compatible with? The manufacturer says that Evolution Gun Works Officers Mainspring Housing 25 LPI is compatible with 1911Evolution Gun Works 11413: Officers Mainspring Housing 25 LPI 1911 Steel Blued Carbom Finish Blue