The 5.5" and smaller Tilton clutches require a 38mm contact diameter clutch release bearing on the Annular piston. The Tilton piston allows this conversion for the Saab based release systems, while the Taylor Race Engineering Conversion Kit works on the 1999/2000 Van Diemen. Note: Some minor modifications required. Instructions included with Piston Adapter kit. Tilton Piston is also used to install 38mm bearing in 1990-1998 Van Diemen cars using 5-1/2 Clutch. Call for details.