Crosman Piston Spring Fits Crosman Optimus models CO8M22X, CO1K77X and CO1K77 Fits non Nitro-Piston Crosman Phantom models: CS1K77 and CS1K77X. Does not work with the Youth Raven breakbarrel. Replace the worn spring in for your Crosman spring breakbarrels. Get your gun back in shooting condition and pick one up today! Tech Tip: Crosman informed us that this spring would work with most non-Nitro-Piston Breakbarrels, but not the Youth Raven Breakbarrel which requires a specific spring.