for Lambretta 125 LI/ Special/ DL/ GP/ 150 LI/ Special/ SX/ DL/ GP/ 175 TV2??-3??/ 200 TV/ SX/ DL/ GP 4 mm aluminium for tuned engines Product description A base gasket surface spacer , or packing-plate , sits between the reed-valve and the cylinder. The use of this 5mm thick aluminium packing-plate from TD-CUSTOMS fully opens the boost-port. Without its help the frame surrounding the reed-valve petals obstructs the function of the boost-port. Do not forget to order a new MMW reed-valve block.