When you shift from the big-to-small chainring, the chain guide can effectively prevent the chain from falling when shifting. MUQZI Chain Guide.
Cryfokt Single Speed Chain Tensioner CNC Machined Aluminum Alloy Bicycle Chain Stabilizer Easy to Install for Folding Bike Single Speed (Red)
Durashmall Aluminum Alloy Chain Tensioner for Brompton Cline Pline Folding Bike Single Speed Internal 3 External 4 5 6 7 Speeds Rear Derailleur Guide Wheel Black(Black)
Aluminum Alloy Chain Tensioner Adjuster withCycling for Folding Bike Single Speed Bike (Black)
1PC Folding Bike Single Speed Chain Guide Clamp Adjustable Anti-Drop Protector S
ERYUE Folding Bike Chain Stabilizer Durable Single Speed Chain Tensioner for Bike Single Speed Folding (Black)
Chain Tensioner for Brompton Folding Bikes Single Speed, Fits 3 to 7 Speed Setups, Aluminum Alloy Compatible with Cline and Pline Folding Bike Models (All Black)
