Rear Brake Drum Measurement inside or outside?

rarichard said
Ordering some new rear drums for my 74 swinger. slant 6 with 3 speed auto transmission. When they ask for 9 or 10 inch rear drums, are they measuring inside shoe surface diameter? or are they asking for outside diameter across lugs? Thanks

And turning your old ones would be best if possible. New stuff is junk and also should be turned before putting them to use.