Patented recoil protection. The Mag Shield: designed to provide vital recoil protection while sighting in or doing benchrest shooting. Excellent protection for mid-range centerfire rifles. Recommended for calibers up to .300 Win. Mag. Mag Plus Shield: designed to provide same recoil protection as the Mag Shield but the heart-shaped design provides additional protection for upper arm area & creates more surface area to dissipate recoil energy better. Super Mag Plus: heart shape design provides superior protection for shoulder & upper arm Highest protection level. Field Shield: designed for the field shooter. Lightweight patented foam recoil system is designed to allow quick easy gun mounting in the field provides valuable protection.