Later two more second-hand shunters from Czech Republic industrial railways were also bought.

Currently there are fifteen locomotives in service with Serbian Railways while another two are operated by the rail transport division of the Kolubara coal basin.

Two 621 series locomotives operated by Rail transport of Kolubara coal basin are painted in green-yellow-black livery.

The nickname "Teletabis" (Telletuby) cmes from the fact that the locomotive having a somewhat boxy and cute shape, similar to the characters from the show.

In game the locomotive is classified as DE2 (Diesel-Electric with 2 powered axles) and is usable after the player has completed the tutorial.