Really Right Stuff's ARC-LR provides a durable and secure solution for mounting your gear to a tripod. It features a RRS-Lock System that uses centered-indexing and safety-stop features to compatible RRS 1.5" Standard rails and clamps, preventing unintentional movement with a 5mm steel pin. The R-Mount interface prevents twisting and play between ARC-LR and RRS head, ensuring stability over time and an easy top-loading design allows quick transition from closed to fully open clamp positions. Other features include a visual lock confirmation that instantly verifies clamp status and an adjustable clamp tolerance accommodates various 3rd party Arca-style plates or rails. Features: RRS-Lock System adds centered-indexing and safety-stop features to compatible RRS 1.5" Standard rails and clamps, preventing unintentional movement with a 5mm steel pinR-Mount interface prevents twisting and play between ARC-LR and RRS head, ensuring stability over timeEasy top-loading allows quick transition from closed to fully open clamp positions for effortless attachmentVisual lock confirmation instantly verifies clamp status for added peace of mindAdjustable clamp tolerance accommodates various 3rd party Arca-style plates or rails for enhanced versatility Really Right Stuff Adjustable R-LOCK Lever-Release Clamp ARC-LR