| 摘要 |
<p>The glass of the facemask is secured in a plastic frame whose rim is provided with a series of holes from front to back. The rest of the facemask cover is moulded to the frame, with beads of material keyed into the holes, to form a smooth watertight fit. The glass frame is made from hard thermoplastic while the rest of the mask is of soft plastic or rubber. The holes have widened sections at the frame surfaces to aid the keying of the softer material.</p> |
