Full Speed Ahead NO.55R/57-A Headset - For 62mm OD Head tube 1.5" w/TH-874-1 Anodized BLKFull Speed Ahead NO. 55R 57 A Headset For 62mm OD Head tube 1. 5" w TH 874 1 Anodized Black. The Full Speed Ahead NO. 55R 57 A is designed for use with 62mm outside diameter head tubes and features high performance 1. 5" Angular Contact Bearings (ACB) with black seals. For use with 62mm outside diameter head tubes Designed for 1 1 8" to 1 1 2" tapered forks Aluminum top cover 1. 5" angular contact bearings provide smooth movement while the black seals