Gently used 8 Track Tape Cardboard Sleeves.  These still have shrink wrap on them, except for the slot for the actual tape.  Please note with some tapes you may need to remove the shrink wrap, otherwise they may not come back out of the sleeve easily.  These are RCA branded.  Price is $2 per sleeve.  Currently I only ship these within the USA due to their bulkiness.  

8 Track Tape Cardboard Sleeves RCA Brand