completely unnecessary. RFID needs to pass through the card to get a read. If you have more than two cards with the feature in your wallet they will scramble each others info. If you are still worried about getting skimmed, or you only have one RFID card, cut a credit card sized piece of kitchen foil, then reinforce it with duct tape. Keep that in your wallet so its footprint overlaps, or partially overlaps the RFID card.
It will block all data, no worries. If you don't believe it works, it is an easy experiment to test at home.
Had again! I do however dig the layout of the flip side and the functionality. I can't wear one in the back pocket because of back issues. Carries like a flip phone. Thanks for the education. So I guess I am protected as long as I have more than one card juxtaposed in any type of wallet.
I received one from my tin-foil-hat wearing father as a gift for Christmas last year and it's still sitting in it's box in a drawer. I've become a big fan of minimalist wallets and the thicker tri-fold monstrosity he bought me just doesn't do it for me any more.