Review on Kentek Lot of 10 USB Type A Dust Cover with Handle Port Protectors - Black for USB Female Ports by Jim Worthington

I use both rubber and plastic. Both have their favorite situations. They are made of hard plastic and have a protruding edge. This makes them very easy to uninstall and reinstall in situations where you frequently connect/disconnect something. I was concerned that hard plastic wouldn't fit as snugly as rubber, especially on different devices with (probably) different tolerances. They are perfect for any device; they are tight but not tight. In some situations, the protrusions can catch on objects. For example, if you rub a knitted sweater against one of these, the bulge will hang in the sweater. Rubber caps have a lower profile (no bulge or a tiny bulge) and can offer slightly better moisture protection. Rubber caps require more patience/precision to apply and are harder to remove (you often have to poke your fingernail underneath). I've had less success with the fitment of the rubber stoppers (maybe manufacturers don't try as hard to meet their tolerances because the material is more forgiving). I've never seen an SD rubber plug that fits properly and nobody uses these slots so they ALL need to be capped. (I use duct tape for the SD slots)