REV-XP, REV-XR, REV-XU, REV-XS, REV-XM, REV Gen4. Lightweight single runner skis provide virtually effortless steering at low speeds, and constant grip without compromise at higher speeds. Note: The use of aggressive skis, ski carbide runners or studs will alter the handling of your snowmobile, particularly in terms of manoeuvrability, acceleration and braking. Please refer to your Operators Guide for more details.