The Tatra KTNF6 is a modernized tram, type KT4, rebuilt with a central low-floor segment. These types of tram cars are used in Cottbus, in Brandenburg City and Schöneiche-Rüdersdorf, Germany, and in Tallinn, Estonia (as KT6TM). Another similar variant of KT4 is KTNF8 (also called KT4NF), which is used in Gera (Germany).
These trams have new interiors, chairs, doors and middle sections with low floors.
The breakdown of the type designation is as follows: K implies articulated T indicates a powered vehicle NF for Low Floor 6/8 is the number of axles.