I have several F1s and some transit plugs for them but am unsure which plug belongs to which gren... Czech one and Polish PRAC came with full-length red-brown plugs but don't know which the black full-length and short ones belong to (I have other Polish and Russian PRAC types and Albanian one they may be from). Does anyone know which type plugs are associated with any individual country's (or factory's) F1s? Also, the plugs are bakelite, right?