Bont 167 bearings + adapters
The 167 bearing is the only bearing on the market that is designed specifically for Derby. Being small in size, the 167 bearing offers the highest acceleration of any bearing on the market. Exactly what you need in Derby. It is also the lightest bearing on the market which also helps with acceleration. The bearing has double shields to stop dirt getting in and the bearings fits 7mm axles. Upgrade your bearings to the new 167 bearing from Bont. Patent Pending.
These bearing adapters allow you to use a mini bearing in a wheel that was made for a larger 608 bearing. The benefit of using a mini bearing and an adapter rather than a 608 bearing is that you can create a much lighter set up with better acceleration.