Superb quality, virtually no play, used by many F1 and F3 constructors! Aluminum construction except for the steel core which gets welded and/or pinned to the steering shaft. The outside diameter of the core is 1" to slip into a matching hole in the steering column. If the steering column is also 1 inch OD, just add a sleeve over both. Attaches to steering wheel with a compact 50mm three hole pattern using 10-32 bolts (furnished). Special asymmetric spline allows mating in only one orientation so you will never end up with a cock-eyed steering wheel. Releases with a spring loaded sliding sleeve with four locking balls. 20mm splines. FIA and SFI approved.