--NOTE: This bicycle rear derailleur is compatible with Brompton bikes only --Keeps the chain tensioned whether the bike is riding or folded --Material: High-quality PC engineering plastic, fine workmanship and wear-resistant --Fine Workmanship: Strictly controlled product quality and specifications during production --Durable: Durable construction for long-lasting performance --After tested: All items are carefully checked and tested by our technical department Name: Chain Tensioner Material: PC engineering plastic Weight: 102.3g Compatible with: Single speed, internal 3-speed, external 2-speed, internal 5-speed, internal 8-speed Packing list: 1 x Chain Tensioner Note: Due to manual measurement, please allow 1-3 cm error Due to screen and other objective factors, there may be a slight color difference