This is a bulk pack of custom designed thank you notes for sellers.  They are A2 size - An A2-sized card is 4.25in. x 5.5in.  These are designed and printed in my art studio, West Hills Studio.  I made these because I need them too, and it’s nice to put a personalized note in orders.  The back side is blank for your personal message, or just send it just like this.  This pack does not come with envelopes, if you are interested in a pack with envelopes, that is $50 for a pack of 40.  If you are interested in larger quantities, message me and I can put together a custom listing for you.  
These are hand designed and printed, so slight variations can occur, although I inspect each one for quality.