PAIR OF 2 New old stock genuine Serotta derailleur cable downtube barrel adjusters w/ springs and washers
These were the ones that were proprietary to the newer style Serotta frames that are becoming harder and harder to find. 
Includes springs and washers as pictured, I have another listing for these without springs and washers if you don't need those. 
Machined alloy
M6 coarse thread

I have lots more Serotta stuff - let me know if you're looking for anything specific.