The Sinclair Shoulder Bump Gage Insert #45A is a precision measurement tool specifically designed for 45-degree wildcat cartridges providing accurate shoulder positioning measurements for reloading applications.Sinclair Shoulder Bump Gage Insert Model #45ADesigned specifically for 45-degree wildcat cartridgesPrecision measurement tool for cartridge shoulder positioningEssential component for accurate reloading workThis specialized insert ensures consistent and precise measurements when checking cartridge shoulder setback making it an essential tool for serious reloaders working with wildcat cartridges.