Aprilia head light socket for 1950's and 60's Italian Motorcycles. This socket takes the regular 20mm bulb and fits into the 44mm hole in the back of the reflector. The socket is held into the reflector by 2 spring steel flat clips on the sides. There are lots of different sockets and this is just one of the many used and PLEASE check your existing part before ordering. NOTE: Out of production for the last 3 years and now available again at only double the previous price.