This is a great deal for some USMC used surplus. IIRC, it's polartec 100wt fleece. Seller looks to have many.
My current one in the foliage green color weighs 1.2oz and is probably my favorite/most comfortable 3 season beanie.
Just picked up another one in Black. Enjoy!
Note: they are only $10 brand new at cabelas, but shipping will add a good chunk.