This chain adjuster can turn a multi-speed bicycle into a single-speed bicycle. The spring design can be adapted to gears of various sizes to prevent the chain from slipping out of the crank. This chain adjuster can turn a multi-speed bicycle into a single-speed bicycle, ensuring the perfect tension of the chain, allowing you to pedal more easily This transmission pulley guide is light and small, easy to install and use This single-speed bicycle adjuster is suitable for folding bicycles with 11T or 13T rear derailleur. It is a great accessory for cycling enthusiasts Product Bicycle chain tensioner folding bicycle single speed converter bicycle rear derailleur chain guide speed regulator accessory : This chain adjuster can turn a multi-speed bicycle into a single-speed bicycle. The spring design can be adapted to gears of various sizes to prevent the chain from slipping out of the crank. This chain adjuster can turn a multi-speed bicycle into a single-speed bicycle, ensuring the perfect tension of the chain, allowing you to pedal more easily. This derailleur pulley guide is light and small, easy to install and use. This single-speed bicycle adjuster is suitable for folding bicycles with 11T or 13T rear derailleur. It is a great accessory for cycling enthusiasts. Specification: Material: Aluminum Alloy Color: black and red Accessories: suitable for folding bicycles with 11T or 13T rear derailleur Weight: about 63 grams Packing list: 1 x chain adjuster