Springfield Armory Echelon 4.0C Slide Assembly Black. O.G. (Central Operating Group) for unmatched modularity across the platform. Whether upgrading a full-size Echelon 4.5 or converting the smaller more concealable Echelon 4.0 into a full-size configuration these kits are the ideal upgrade. Specifications for Springfield Armory Echelon 4.0C Slide Assembly: Manufacturer: Springfield Armory Gun Make: Springfield Armory Caliber: 9mm Luger Color: Black Fabric/Material: Steel Package Contents: Springfield Armory Echelon 4.0C Slide Assembly Springfield Armory EC0309C-RET: Echelon 4.0C Slide Assembly Black