The Petzl I'D-S (small) is similar to the RIG but has more built-in safety features like the anit-panic lowering control and the anti-error rope installation cam (stops incorrect installation of the device). The Petzl I'D-S works on inertia, similar to your car safety belt. The button on the bottom of the handle allows for horizontal or low angle movement without engaging the cam. When used as a lowerable ground anchor device for single line access the anti-panic feature means less qualified personnel can lower the climber if the need arises. Check for access rope campatibility before investing in this product.