A full-on 200m blast. Above this section there is reputedly a 2km of grade 5/6 gorge if you fancy trying your luck.
Takeout at Trericket Mill bridge just before the confluence with the Wye (just off the A470 between Llyswen and Erwood). From here simply walk 200m up the river and have a quick blast down.
Rainchasers is best experienced as an app.