Our stage one plenum is CNC  machined from billet 6082 aluminium. It is ultra light due to being only 3mm thick, yet has been tested to over 35psi. All of our plenums feature a removable boost pipe fitting so you can choose from either a 2" or 2 1/2" boost hose, plus a built-in, 40mm blow-off valve.
 
The key feature of these plenums is that they seal directly down onto the throttle bodies with o-rings and a clamping arrangement, so there's no need for silicon hoses and fiddly hose clips. The plenum chambers can be mounted either way onto the engine if using our adaptor sleeves (sold separately), which makes them incredibly versatile, so can be made to fit any installation be it a car or a bike.