The Prometheus Flat Hop Up Tensioner is designed to be a practical drop in flat hop nub. It comes with both a Purple/Blue soft tensioner piece and a black harder tensioner. When coupled with one of the Prometheus straight chambers you have a drop in flat hop setup. While it isn't as good as using the traditional setup it is very comparable and the convenience can't be beat.
Prometheus is one of the top upgrade companies known for their high end barrels and hop up upgrades. Based out of Japan they've been releasing airsoft upgrade parts for over a decade and are a tried and true name.