Viscosity Grade 20, Synthetic, 1 Liter Bottle, Single for Fork System Upgrade and Adjustment Fork oils with a high viscosity index (HVI) are designed to operate consistently across a wide temperature range. An efficient and affordable technique to adjust the compression and rebound of conventional forks without making hardware adjustments accommodates various rider weights and circumstances contains anti-foam ingredients to keep compression and rebound predictable in difficult conditions and to avoid aeration. Enhancing fork seal performance using additives