After wrecking many sets of BC flip ups and one or two ofthe Polar type - eventually went for the Bikini style rubber covers by BC.
370756374997 on the auction site.
Held on the scope by a couple cable ties around the tube, they WORK and do not break.
Waterproof, quiet and fit any scope. Pricey initial purchase, but have not killed a set in three years of daily use.
Recommended option.