Three formats for door-to-door distribution. These are read by someone standing at their own front door with keys in hand, deciding in about two seconds. A harsher filter than almost any other printed piece faces. Filter by how much the message needs to say.

4.25″ × 11″. The offer needs explaining.

3.5″ × 8.5″. Volume distribution, cost per piece.

Your size, shape or coupon: a shape, a tear-off or a special handle.
If the offer needs explaining (a service, several options, a price comparison) the full 4.25 x 11 gives room for a headline, detail and a coupon without crowding. If it is one line and a phone number, the compact format achieves the same thing across the same number of doors for a lower unit cost, and at volume that difference is where the budget goes furthest.
Two practical points. Whatever the size, who it is from and what the offer is have to be legible at arm's length without the hanger being picked up, or it goes in the bin at the door. And these are left outside, often overnight: coated card handles damp air, but sustained rain needs lamination or a synthetic stock. Choosing that by season is cheaper than reprinting a run that turned to pulp.