@raclut a cashier at Costco told me to keep my Costco Citi Visa in a sleeve. I am not versed in this technology at all (so my terminology may be wrong), but there is a little “sound” icon on the right side of the chip that indicates that the credit card puts out a signal; I was told that the signal from the card helps make credit card transactions faster. Apparently the credit card’s signal can be electronically picked up by thieves when you are standing near them and they can steal your credit card number. I checked all of my credit cards and my Costco Citi Visa is the only one that has this little “sound” icon.