My B&L Stereozoom microscope didn't have any protection for the objective lens assembly. It uses a rather oddball 38 mm threaded mount. I thought that those with the same scope might be interested in the adapter being sold as eBay 401250097157. It fits the 38mm thread on the B&L perfoectly and adapts it to a standard 52mm filter thread. Cheap--less that $3 shipped. Just got it today and it fits like a glove. FWIW --Chuck