The Bulgarian is a factory chrome lined 5.45X39 AK74 Barrel pulled from a New parts kit. The gas block journal is the smaller diameter @ .5895" so you will need to use a smaller journal gas block to use it. $280 for this one
The AK-12 barrel is an Obstreporous Chrome lined 5.45X39 AK-12 barrel that was used for a couple hundred rounds and then the owner decided to switch to 556 and pulled the barrel to swap calibers. $300 for this one