SR= Side reversed to interlock your cards.

6 credit card pockets plus  an extra 4 cards sleeves under the credit cards panels (10cards)

2 Back separated inside compartments for your currencies and invoices.

US= specially designed Like the No 720 SR but for $US currency 1cm narrower called:

No 720 US SR

My most popular gentleman's wallet, made with handcrafted Premium calf leather, fully leather lined with goat skin leather. Suitable for any $ US currencies and credit cards with 2 back compartments, it fits comfortably in your back or front pocket.