Hi john d, do you mean a 2.5mm hole? I don't think they do a drill that is a quarter of a millimetre. Philread your thread on boot opening,i removed the small plug and drilled a 0. 25mm hole through the centre of the plug and screwed in a chrome mirror cap head, (you know the ones you put up mirrors with) works perfect every time so far boot opens fully such a simple 10min job. many thanks.