I have an issue with buying the right size external circlip- this is all to repair an old brass door knob.

The diameter of the groove that I need the circlip to clip around is 0.550", so I thought a 14mm circlip would suit, and ordered a pair from eBay. These arrived and the unsprung diameter measures 12.8mm- no chance of these stretching sufficiently to go on, let alone fit comfortably.

I contacted a bearing supplier, described the precise clip I require, and they explain the notional size of the circlip sometimes is the maximum diameter the clip will stretch to while fitting, and others sell them as the relaxed size, which may explain the issue. So I purchased a pair of 15mm which should have an unsprung size of 14mm at their recommendation, and the clips I received were identical to the previous, although came in a factory sealed packet that says "15mm (13.8mm)" but measure unsprung as 12.8mm.

Have I missed something obvious? Should I just force the clips open, have I bought the wrong clips twice despite being labelled differently? What should I ask for to receive an external clip with a relaxed inner diameter of 14mm?

Thanks to anyone who can help! Richard