I've always used a Ford paper type ones, which I've not always got to seal first go, but, when I worked at Fors years ago, kept a stock of a few spares for mine and my old mans car. As I'd run out and faced with buying a new one at full price, I changed it for a Cometic one this time. Got it on eBay from DS Motorsport. I'm local to him and collected it, he knows his stuff on Cosworths on RS200's.