LARGE Hatchlift Kits are designed to fit light weight RV doors that measure from 33" tall to 38" tall (approximate). One kit will operate doors up to 26" wide. Doors over 26" in width should have a kit installed on both sides. NOTE: Some larger RV doors have reinforcement and are heavier doors. If you are unsure, order the HLK – HEAVY kit or call us to order the correct kit size.