You bond them on with sealant or somthing similar and then screw them in for extra secure fit i presume? It looks sweet on a white st with gloss black grills!
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Colorado Red 07 Plate ST

Mountune CAIS - 60mm Throttle Body - Full Resonated Milltek System - Bilstein B12's - 300mm front discs - Gloss Black Team Dynamics Pro Race 3's - Tints - Red-Black DMB Badges and loads of eBay stuff...