Originally Posted by StephenC

standard rs turbo glass is 3mm. Most of the polycarb windows you buy are 4mm and I think certain race regs also call for 4mm. Should still fit in the rubbers the extra 1mm. Perspex will scratch bad but can polish out, polycarb also scratches but wont polish out. Polycarb is near bullett proof, perspex WILL crack under any decent impact. Im making some polycarb ones this weekend hopefully if the gear turns up.