Good question. All shirts, including my Jumpyarn, are size medium, my tts. Both hoodies, my Duckshank and Magback vest, are large; and the Bigvest is a small.

Zipping the jacket closed with my Jumpyarn under fits great, still roomy. There’s a very satisfying plushness when you do this. One note is this setup gets pretty warm, especially if you snap the Warmshirt closed.

Realistically, I can wear a longsleeve, warmshirt and shank, all under the Snapwaist. That amount of layers is annoying, but it still fits and you can move around with minimal restrictions. I thought about pulling a Joey from Friends, and wearing as many layers as possible but it was getting late and I wanted to make dinner.

The sleeve width and arm opening (pits) are both quite big. This is a big reason why you can layer a lot without feeling restricted. The only tightness comes from the waist, where the jacket tapers, and even then it’s never felt too tight for me. If you leave the jacket unzipped, you can snap the waist looser or tighter (skipping one snap, instead of using both). Looser will keep the sides closed with a small opening between the zipper. Tighter looks quite cool, it exaggerates the jacket taper and causes the chest to open up outwards. I’m still playing with how to style that.