Helping a buddy out, he has a Gen V model 21, and apparently gen 5 and later the G21 locking block and barrel dimensions are different than for the earlier generation .45 caliber guns.  He bought this brand new, but threw away the package and it has been too long to return it to the store, it locked up his gun when he tried to install it, and after many months I looked at it and got it apart.  Basically a gun store screw up.

OEM Glock, 16-1 metric LH threads, brand new, with just a finish ding on the locking area from it being assembled for a gun it doesn’t fit.

Willing to trade for a good brand G21 Gen 5 type barrel, with RH thread pattern.  (None of the no name/cheap brands.)

Sell for $160 shipped OBO, then I will just buy him a correct barrel.  

My buddy has terrible luck with brand new weapons, so let me help him get squared away and able to use his suppressor!

IM with any questions or offers.  Will get pics up soon.  

This barrel does have a serial number, I believe what happened was Glock imported a number of Gen 3 or4 guns with metric LH threaded barrels, but they sold poorly, so they replaced the barrels with standard ones and sold the pistols long ago, and are still selling off the stockpile of OEM LH threaded barrels.