We can thank the 90s for the revolution of the single crown fork, and we can thank Marzocchi for their improvements that resulted in the Bomber Z1 27. 5 Coil Boost Fork. A sturdy and reliable 36-millimeter chassis is a given off the bat, and the brand boasts their most advanced coil spring system with the Bomber Z1. Their new coil system also features an uber-lightweight tempered silicon-chromium steel spring thats paired with near-silent performance due to its noise management system.