Installation of Ring Doorbell 3: what size Rawl Plugs

Hi, I've mounted my doorbell at 'normal' height, nowhere in the instructions did it say to mount at 120cm high so every time the bus goes past I get a notification! I can't get the rawl plugs out... what size are they? In the UK Rawl Plugs are mostly colour-coded and the Ring ones are clear and I have no idea how to measure them.