Please note: The solid plate cog set up can only be used on bikes that already have them, If your bike has a cog set up with a clutch the control unit would need to be replaced or re-programmed by us to work with the solid plate cog set up. All 18" and 20" Revvi bikes can use the cog set up with a clutch, even bikes that were supplied with a solid plate cog set up.
 
Image attached shows the difference between solid plate and clutch cog set ups.