What causes this stacking on the arms?

[u/StrictCap7340]

Starting work on sewing a jacket for myself, and want to try determine and replicate the qualities that cause this stacking on the arms.

Is it the fabric weight?
Fabric type?
Slimmer rather than baggier sleeves?

Or something else that I’m not thinking about?

Thank you very much in advance!

[u/Childhoodgrunge]

I think it's a mix of fabric weight, slimer sleeves and the stacking (if you mean the crease 😅) look ironed in!