Most manufacturers use a sort of flexible plastic "blow molded" out of flat stock. There's a general perception that lenscaps should be inexpensive. (When the U.S. Navy spends $150.00 for a lenscap its considered one of those government contractor corruptions.)
So its difficult to justify the added expense of a really good lenscap on an already high priced product.
See: My lenscap page for some pictures of these.
Although your experience with the light duty caps is not an everyday one its cerainly not unusual. I make custom lenscaps of Delrin or other rigid ABS plastic which are more rigid than the usual blow- molded factory originals.
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