The INA hydraulic belt tensioner (534015910 / OE 11288620210) is a supercharger accessory-belt tensioner designed for supercharged MINI Coopers, where — unlike most vehicles — the accessory belt tensioner also applies tension across the supercharger drive. It features a high-tension spring assembly, precision bearing, and durable cast housing to restore proper belt tension and eliminate slip-related noise.

Fitment: MINI Cooper S and John Cooper Works (R52/R53 chassis, supercharged W11B16A engine), matching the source's stated fitment.