"The outside diameter of these collars are about 50mm; a bit bigger than some others on the market, which in my case was what I was looking for.
A bit more product information would be nice, Screwfix... These are "Polypropylene collars with Chrome effect coating" (quote from the Talon web site). Saying that - the outside diamater isn't even on Talon's site... These things are of interest to customers you know."