The ACT 6-Puck Sprung Hub Race Disc is SFI certified, so it is legal for all forms of racing that require SFI compliance. An ACT G6 race disc has a very durable friction surface with good spline life. The G6 was designed for a highly modified car that is drive to, on and from the track, as long as harsher engagement is acceptable. The sprung hub helps to reduce driveline shock and be relatively quiet compared to an unsprung hub, though the G6 can still be noisier than a full face disc and will have some chatter.