Neither seller nor manufacturer knew the size of the thickness. After several emails I was told that it would hold items 2" to 2.5" thick. It turns out that the maximum is probably just under 1/2 inch.
Credit Card Holder with Chain Cover
70 Review
Wally Micro Reversible Wallet Pull Tab Men's Accessories and Wallets, Card Cases & Money Organizers
53 Review
Maxpedition BRK π³ MX218F Gear Micro Wallet
68 Review
BRASS TACKS Leathercraft Handmade Blocking Men's Accessories and Wallets, Card Cases & Money Organizers
89 Review