Replacement old style partial flush button, diameter across outer chrome collar is 47mm. Oli have modified the bellows canister on the back of this button. The button we send you, though visually different, will work, but only if you have the new style flush valve and control block (see photo 2). If you have the old style versions, you'll also need to buy TS324 & TS333 in order for the modified button to work. If you're not sure, please email a photo of the inside of your cistern and we will advise.