I got one of these USMC surplus grid fleece pullovers last month from the Sportsman's Guide and have worn it a lot since then. SPG has the best price I've seen on them in unissued condition.
I use it as an insulating layer under a windproof shell, either my First Spear Windcheater or German surplus flecktarn parka. I've also worn it as extra insulation under my Arc'Teryx Atom LT and SV hoodies on really cold days.
It's a light weight, half zip pullover that can be used as a base layer or on top of other layers. It is remarkably
warm for its thickness and weight. The outside is pretty smooth
but the inside is a polar fleece with a grid pattern in it that traps a
warm air layer near your body. I just took a walk wearing it over a
t-shirt and button down shirt, under the flecktarn parka on a walk
around my neighborhood. It's 27 degrees and I was plenty warm.
The one I ordered is an XL. It runs a little big based on my sample of one. That's OK because as a pullover, it's more difficult to put on or take off compared with a full zip sweater, and the extra room helps.
Two big thumbs up.