DeFeet UnDWool Merino base layer

The DeFeet UnDWool is a really warm base layer yet is thin enough to comfortably sit beneath several layers without adding much bulk. The price does place it at the upper end of what we'd expect to pay for a base layer though.

The base layer is made from Merino wool which is my personal favourite base layer material when it comes to keeping warm in the winter. This is quite a thin base layer so it will serve you well in warmer temperatures, but the insulation provided is decent consider how thin it is. It's a very fine wool, and is exceptionally soft next to the skin.

Incidentally, DeFeet gets its Merino from sources that don't practice mulesing of the sheep, a controversial technique of preventing fly larva infection that some campaigners say is cruel.

Despite its lack of bulk, DeFeet pitch this as their warmest base layer in its UnDSystem range, and my testing certainly backed this up. On a recent ride with a temperature hovering between 5°C and 7°C, and just a lightweight softshell over the top, I was adequately warm.

Fit is important in a base layer and in this respect the DeFeet does well. I'd describe it as a slim fit. The size medium tested isn't skin tight, instead there is a bit of bagginess which increases the comfort. And also means you can wear it off the bike as a t-shirt quite happily. The length is generous so that you get a nice underlap with your shorts or tights.

I tested the short sleeve version, which is a more versatile option than the long sleeve version that is also available, though for the coldest winter days the longer sleeves would be an obvious bonus. The construction uses raglan sleeves designed to eliminate uncomfortable shoulder seams. Certainly none of the seams are noticeable when you're wearing it.

There's very little branding, just the small DeFeet logo on front of the collar.

Verdict

Soft, comfortable and warm merino wool base layer.