What size is this jacket?

It is labeled large. The measurements are about 25 inches armpit to armpit, 22 inches armpit to cuff and 25 inches collar to hem.

Nothing states a waterproof or water-resistant finish. Treat it as a warm layer for dry, cool days and check the fabric before wearing it in rain.

It is insulated, so it adds warmth over a shirt or hoodie. No fill weight or temperature rating is given, so it suits mild to cool weather rather than deep cold.

How does it fit compared with a regular large?

The 25-inch pit-to-pit width is generous for a large, so expect a roomy, boxy fit. The 25-inch body length is short and sits around the waist.

What can I wear under it?

The roomy cut leaves space for a hoodie, flannel or sweater. A bulky midlayer should still fit given the chest width.

Is it good for hiking?

It works for light outdoor use in dry, cool conditions. For wet trails or serious cold, a shell with stated waterproofing and a fill rating is the safer pick.