Patented recoil protection. The Mag shield: designed to provide vital recoil protection while sighting in or doing benchrest shooting. Excellent protection for mid-range center fire 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..