"These end caps are for smaller dia roller sleeves than standard, presumably purdy's own, which Screwfix don't stock. I couldn't find anyone else who stocked them either. I bought these because I'd bought the Purdy adjustable frame and some standard rollers flaled about on it making rolling like driving on a flat tyre. The Purdy end caps fit like a bearing onto the frame but are as useful as a hat rack to a moose without roller sleeves. Screwfix is not alone, other retailers also stock the Purdy frame and standard roller sleeves. The trick is to clamp the frame in tight on the roller, not ideal but usable."