This single speed chain tensioner is designed for folding bikes with 11T or 13T cogs. It enables a reliable, easy conversion from multispeed to single speed while keeping correct chain tension. Key benefits - Compatibility for folding bikes using 11T or 13T cogs and a range of gear sizes thanks to a spring loaded design - Reliable performance with a spring mechanism that maintains constant tension as the chain length changes - Efficient pedaling with proper tension that reduces effort on flats and gentle climbs - Easy installation and maintenance with a compact, lightweight unit - Durable construction built to withstand repeated use in daily riding - Minimal footprint that does not interfere with folding or shifting Use scenarios - Daily city commute with a folding bike; switch to single speed to simplify maintenance and reduce shifting in stop and go traffic - Weekend rides on mixed terrain; use single speed to maintain predictable chain tension across different gears - Travel or touring with limited luggage space; convert drivetrain to single speed to lower component count and improve reliability In short, this tensioner simplifies drivetrain setup, enhances chain control, and supports reliable performance on folding bikes across common riding scenarios.