The Umarex Hammer is a serious big bore air rifle that needs serious ammo. The UX SLA series ammo is custom-made just for the Hammer's .510 diameter bore. For great overall performance, this 320-grain hollowpoint is a perfect match. Expect velocities for this round to be in the 940 FPS range which will translate to over 640 ft-lbs of energy at the muzzle. These SLA slugs are sold in a 20 count box. Features320 Grain Hollow Point SlugMade for the Umarex Hammer PCP RifleFlat BaseSmooth Sides20 Count Box