These Phonak Power SlimTubes are for use with Phonak BTE hearing aids and a custom earmould - a dome will not fit on a Power SlimTube.
Phonak Power SlimTubes have a 'female' thread fitting onto the hearing aid. The thread is slightly smaller than on a Power SlimTube II and does not have a slot across the hearing aid end. They are marked at the hearing end with a number indicating the size in red (for right) or blue (for left).
Phonak Power SlimTube fitting guide