A twin-action rear shock absorber for the Yamaha MT-09 21-22. YSS introduces the new 506 RTL rear suspension through the Z Series range. This is a new high-performance suspension unit, nitrogen - oil, with adjustment of the spring preload and the rebound damping. This particular range is fully rebuildable. Suspension Type: With a Single Nitrogen Oil Chamber Rebuildable: Yes Suspension Type With a Single Nitrogen Oil Chamber Shaft Diameter 16 mm Spring Preload Threaded Piston Diameter 45 mm Suspension Length 330 mm Rebound Adjustment Yes Compression Adjustment No Length Adjustment +/- 5