I carry (usually) two lenses. The first one has a screw-in rear metal cap. The front cap is a snap-on plastic kind, and i have one of those giant wide extra-strong rubber bands that goes over the lens (front to back) to keep the front cap on. This goes in one of those $10 velcro-corner lens wraps. The other lens gets the plastic cap and rubber band treatment on both sides, and the lens wrap also, but gets stuffed in the bellows of my disassembled camera.
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