Assertion: trachea's ring | /r/HasProperty | semi-rigid plastic material
Facets:
Source sentences:
text: The rings 22 may be of a semi-rigid plastic material; their number, dimensions, and spacing are not critical so long as they provide adequate radial support for the collapsible section 21.
text: The rings 22 may be of a semi-rigid plastic material; their number, dimensions, and spacing are not critical so long as they provide adequate radial support for the collapsible section 21.