We're still digging out the new inventory, and the next addition to the Solarbotics lineup is the RW2i, which is the same profile and rolling size as our very popular RW2, but is designed with a narrow hub.
We're able to do this by moving the set-screw hole inside the hub, so to cinch the screw down, you have to remove the tire from the hub, which is a pretty easy process.
We had planned to make the internal cut-out of the RW2i to allow the installation of a GM11a-14a style motor to the open side, but the manufacturing tolerance was a wee off, and we can't quite make them fit. Fortunately, it's a pretty simple process to file the edges of a GM11a-14a motor to make it fit, which has the added benefit of making the brass edges of the gearbox act as brass bushings that assist wheel alignment.
Also new to the RW2 and RW2i wheels is a new hole diameter! We've had many requests for alternate shaft sizes, so we had a limited portion of both these hubs manufactured with a 1/16" pilot hole so you can drill it out to whatever size you need!