Assertion: snorkel's mouthpiece | /r/HasProperty | formed with an upper
Facets:
Source sentences:
text: 2, 3 and 7, the mouthpiece 31 is formed with a hollowed bit 33 to be retained between the upper and lower teeth of the user, and an arcuate retaining hood 35 including an upper and a lower flange, 36 and 37.