The 5.5 × 2.85 in tri-fold
A half-letter sheet folded twice across into three shallow bands — six panels in total, closing to a piece about the width of a hand.
Closed size5.5 × 2.85 in
Opens to5.5 × 8.5 in
Panels6
FilesLayered PSD, smart objects
Small enough to travel inside something else, which is mostly where it turns up: care instructions and warranty slips packed with a product, ingredient and dosage leaflets, festival and museum guides, loyalty and punch cards, mini menus and wine lists that sit on a table without taking it over. It's also the tri-fold that fits a card envelope, so it posts as an insert rather than a mailer in its own right.
The real limit here isn't panel count, it's type size. Six panels sounds like plenty until you take margins off a band 2.85 in tall and find room for a heading and a few lines — and text can only shrink so far before it stops being readable in a hand. So this format caps content rather than compressing it: pick what actually has to be there and let each panel carry one thing. Anything longer wants a bigger sheet, not smaller type.
In the sets: closed, mid-open and laid flat from above, so you can present the folded piece and the full open sheet together. Each is a layered PSD with smart objects — the artwork sits on its own layer, so replacing it leaves the folds, lighting and shadow untouched.