These bearing adapters fit over your Bont mini 167 bearings so they can be used in a regular-sized 608 wheel hub. There are two advantages to using mini bearings. These bearing adapters are made of aluminum.
1. You create a much lighter setup as a 608 bearing weighs 12 grams compared to a mini bearing at 4 grams and an adapter at 1 gram.
2. Mini bearings spool up faster than regular 608 bearings.
You need 1 adapter per bearing.