Genuine correct length with cut outs and drain holes in the correct places.
The MK3 door seal is notable because of it's large 'bulb' area. The 'bulb' is the round section that the door closes against. The size is determined by how much gap the door leaves. If the bulb is too small as is found on the MKI and II then the air rushes in. If the MK3 seal is used on a MK1/II then the door is VERY difficult to close!
These are not just cut lengths of rubber as commonly sold by accessory shops and most mini specialists. These are original type seals with the correct and exact cut outs and air/drain holes which make them so easy to fit. These were fitted up to the introduction of the twin point cars in 1996 which then use a split type to hold the trim in better, but these can be used if on a budget.
From 1996 on MPI cars used CFB101090 L/H and CFB101080 R/H for the lowers and CFB101120 R/H and CFB101130 L/H for the uppers.