René, just checked and the Mini grease nipples you link to part #UHN445, are ¼"UNF so would fit. The thread doesn't look too long so should be ok. You could always add a washer if needed.
Richard
2018 Roadster 3.7 1966 Land Rover S2a 88 2024 Royal Enfield Guerrilla 450 1945 Guzzi Airone
