People give fibreglass a bad rep because there so you used to getting shite made by people who havnt a clue fibreglass can be as good as a metal or plastic pannel it all depends on the materials quality Of the plug and the actual mould its self. It's even used on super cars along with other composites so what does that tell you. The problem is people mould bad quality parts to start then another copy's there bad copy there's point it saying oh it's fibreglasd it needs all this extra work when that's not the case if the said company test fitted the part made it fit correctly remove all defects them moulded it they could produce good quality correct fitting parts with very mirror prep need for paint