Short answer: the dad who wears vests already owns the fleece one and the puffy one, so the gift is the vest he does not have yet: a knitted wool vest he can wear to dinner, to the office, or over a shirt at Thanksgiving without looking like he came in from the trailhead. Buy it in his suit-jacket size, in charcoal if you are unsure, and buy it somewhere the size exchange is free.

I own Ritter, and every November the same email arrives: "my dad lives in vests, what do I get him?" This is the answer I give, including the parts that are not about us.

Start with what he already has

Most vest dads own two or three of the same thing. A fleece vest for the yard, a down or quilted vest for the car, maybe a Patagonia or North Face he has worn for a decade. They are good at one job, which is being warm outdoors, and they all fail at the same point: the restaurant, the office, the family photo. Another one of those is a safe gift and a forgettable one.

The gap in his closet is a vest that is warm but reads as clothing rather than gear. That means knit or felted wool, flat at the shoulder, no logo, no shine, no baffles. It is the one he will reach for when he has to look like he tried.

Five things to check before you buy any vest for him

• Wool, not fleece and not a nylon shell. Alpaca or merino. Alpaca is warmer for the weight and does not itch, because the fibre carries no lanolin.
• No logo. He is past the age of advertising for anyone. A plain chest is what lets it go under a blazer.
• Full zip, not a pullover. Dads run hot and cold through a day. A full zip gets worn; a pullover gets left on the chair.
• Zipped pockets. Keys and a phone stay put. This is the detail dads mention first, every time.
• A free size exchange. You are guessing at his size. Buy from somewhere that swaps it for nothing, and tell him that when he opens it.

Getting the size right without asking him

If he wears a suit or a sport coat, his vest size is his jacket size. If he is between sizes, go down; a vest should sit close, not hang. If you have no idea, look at the tag on a sweater he wears often. And if it is still wrong, that is what the free exchange is for.

Colour

Charcoal never misses. It goes over every shirt he owns and under every jacket. Light Charcoal and Granite are the softer greys. Sandbar and Cocoa are for the dad who wears browns and olive. Glacier, Sedona and Peppermint are for the one who already has the greys and wants something with some life in it. Buying blind? Charcoal.

By budget

Under $40. A pair of alpaca calf socks ($36). Thin enough for dress shoes, warm enough for January. Not a vest, but it is the same reason he likes the vest.

$90 to $150. The three-pack ($87) or five-pack ($145). A week of good socks is a better gift than it sounds, and it is the one his wife thanks you for.

$349. The Alpaca Rittervest. Alpaca and merino, knitted and then felted in Peru so it holds its shape for years, with a plain full-zip front and two hidden zip pockets, in eight colours and sizes S to XXXL. This is the vest for the dinner, the office and the photo. There is a women's cut if mum wants one too.

For the dad who already has the vest. Our EXCLUSIVE line is baby alpaca blend knitwear from the same workshop: a quarter-zip ($265), a cardigan ($215), a shawl-collar cardigan ($335). These are made to order and take up to six weeks, so order by the first week of November if it has to be under the tree.

If you would rather he choose. A gift card, from $25. Not romantic, but he will pick the colour he actually wears.

What not to buy him

A fourth fleece vest. A vest with a logo the size of a coaster. A cheap merino zip vest, which will be pilled by February. Anything described as "performance" unless he actually hikes. And nothing with a hood; a hood is how a vest tells the room it is gear.

Questions I get asked

Will it itch? No. Alpaca has no lanolin, which is the part of sheep's wool that irritates skin, and ours is knitted fine and felted smooth. If it itches, send it back.

Can he wash it? It rarely needs it. Alpaca does not hold odour the way cotton does, so hang it after wearing and spot-clean with cold water. When it needs a proper wash: cold water by hand or dry clean, lay flat to dry, never the dryer.

What if the size is wrong? Free 30-day size exchange in the US with a prepaid label, no email needed, at returns.ritterwools.com.

Will it arrive in time? The vest and the socks ship from Chicago within one to two business days, with free US shipping. The made-to-order EXCLUSIVE pieces are the only ones that need a head start.

If you want the one I make: the Alpaca Rittervest is 34% alpaca, 33% merino and 33% nylon, knitted and felted in Peru, with hidden zip pockets and a plain full-zip front, in eight colours and sizes S to XXXL. Free US shipping, free 30-day size exchanges, and if he already has one, the second colour is the gift he will not buy himself.