I had ordered some extra MR85 bearings with the intention of using one of them to seize up, but I ultimately decided against it. Instead, I searched for 5x8x2.5 plastic spacers and was able to find some that were shipped from Hong Kong. The spacers fit perfectly inside the RBC, resulting in a pleasing fixie response. Additionally, the bearings came with a complimentary pair of mini cones, which makes for a fun photo op.