These low Sako Optilock ringmounts are 1" and made of blued solid steel. Hex key included. Compatible calibers: .17 Rem, .204 Ruger, .222 Remington, .223 Remington, .22 PPC, 6 mm PPC, .243 Win, .260 Rem, 7mm‑08 Rem, .308 Win, .22‑250 Rem, .25‑06 Rem, 6.5×55 mm, .270 Win, .280 Rem, .30‑06 Springfield, .270 Weatherby Mag, 7mm Rem Mag, 7mm Weatherby Mag, 7mm STW, .300 Win Mag, .300 Weatherby Mag, .338 Win Mag, .340 Weatherby Mag, .375 H&H Mag, .270 WSM, .300 WSM, .416 Rem Mag, 9.3×62 mm, 9.3×66 mm, 7×64 Brenneke, 8×57 mm.