Just a quick heads up to those who might be interested; I received these from a company called Richard West Repairs who seem to have access to some UG spares straight from the factory. I had a couple of things on the wishlist (top of which was a replacement upper crown for my Zone Timer - no cigar on that one). These clasps are 16mm for a watch with 18mm lugs; they also have access to 16mm stainless buckles and were even able to offer a bracelet for Gary's big Unisonic. Not sure about 18mm as I didn't ask that question. Obviously these are presumably from the 80s/90s and are not actually contemporary to the watches I have fitted them to; this might bother some people but, on the whole, not too bad for £30 for the stainless and £40 for the gold-plated.