Top quality Lambretta series 3 drum brake fork link buffer set (Original part number: 15060070) with cleaned out threads for bolts to fit all Li models, 125 special and SX150.
Comes as a set of 4 and they are all the same size.
 
Disc models had a pair of slightly larger ones in the bottom and the series 1 and 2 had a slightly smaller one, see other listings for these.