Designed For Use With Semi Trailers Compatible with all semi trailers. Secures opening bars to prevent rear access. Warning: Do not use when the vehicle is in motion. Cargo Containers Use on the innermost opening bars. Cargo protect works on all cargo-containers with or without a central key box. Warning: Do not use when the vehicle is in motion. Box Trailers Compatible with all box trailers. Secures opening bars to prevent rear access. Warning: Do not use when the vehicle is in motion. Shipping Containers Fits all shipping containers from 8ft - 40ft HC. Suitable for overseas and sea shipping, low unit profile allows shipping containers to stacked without interfering with the lock mechanism. Anti Corrosion Double layer anti-corrosion paint, resists rust, enhances strength. End Cap Prevents water & insect ingress into the lock mechanism. Enhanced Flange Design 1/8" steel flanges for higher protection against bar attacks than competitor designs. Reinforced Lock Dual reinforced pin tumbler, protects against hammer attacks.