This is the mainspring also called the hammer spring (mainspring) Winchester model 1892, 1894 and models 64 and 55, 53 PISTOL GRIP lever action rifles. If your lower tang (part behind the trigger) curves down and away from the upper tang (part be3hind hammer) as you move back toward the buttstock then you have a pistol grip. If your upper and lower tangs are parallel then you need part number wp732