This Truma T-piece is an in-line joiner for 65mm hot air ducting with an opening on the side that has a segmented thread to accept an EN end air outlet.

This allows hot air take-off points to be fitted wherever is convenient along a run of ducting and minimises the number of individual ducting runs required around the vehicle.

The segmented threads allow you to push the T-piece over the EN end air outlet first, then turn the T-piece to tighten the outlet against the mounting surface. Lastly, the ducting should be pushed into the ends of the T-piece where it is retained by the moulded-in ribs.