750ml Refill. Leave for up to 1 minute and agitate with a brush if required. (If you are using with a chain cleaning device, unscrew the trigger sprayer and fill the device with the formula). The Muc-Off Bio Drivetrain Cleaner is the complete drivetrain cleaning solution that can either be poured into a chain cleaning device or sprayed directly to your chain rings, rear cassettes and derailleurs to clean your entire drivetrain within seconds.