We use this product to submit payments to subcontractors. Whats great is you can fit not only the check payment but any and all other documents that need to accompany the check. Works great.
The first two cases had glue from the windows leaked over and had to peel each one open to use most times the window was ripped out during the process of almost 30 seconds that should have taken 3 seconds to stuff an envelope.
I bought this product because I could not find the size I had purchased previously. I was disappointed that it's too large for checks (shows amount through window) but too small for invoices.