Full Speed Ahead Headset Lowers Replacement Parts Headset pieces will last a long time, but they don't last forever, unfortunately. Luckily, you can easily replace the upper or lower headset bearings. The Full Speed Ahead Headset Lowers are replacement lower headsets from FSA designed for different types of head tubes. Features Designed for different head tubes Made from durable alloy Comes with a rubber seal | Fsa | Full Speed Ahead Headset Lowers 1 C-40 1. 5 Is52. 1/39. 78 | Rubber