A currency strap, also known as currency band or bill strap is a simple paper device designed to hold a specific denomination and number of banknotes. It can also refer to the bundle itself.
Come in a variety of colors. Ex. Yellow for $1000 all tens, purple for $2000 all 20's, brown for $5000 all 50's, mustard for $10,000 all hundreds.
I pop bands more often than I pop my collar.