This is the last seal fitted by the Rover factory on all twin point injection cars. It sits under the bonnet on the windscreen scuttle panel and down the front wings about 9" each side. It needs the right angle corners to be created when fitting, cut in the rubber area only. The metal seating on the seal will only allow you to cut so far.
This is a great modification to stop water entering the rear of the engine bay and slightly reduce noise on any year mini.