Can't comment on the summer version or the 151s, came across both of them while browsing but my wife had already bought me the knox base layers. I don't feel the need to get anything else for summer. The original ones i have are on sale now as they've released a new pair. Also @Android853sp is right about the collar, it isn't as tall as the heatrub version but way more so than my knox.
I’ve bought a few of these over the years, great quality. You can normally find them in Blacks for about £70.00. https://eu.icebreaker.com/en-gb/pro...-long-sleeve-half-zip-thermal-top-ibb04367013
Iceskin has a collar just ordered one I have used Under Armour for years, now showing its age lol, with collar
My Zero Fit Ice Skin has just arrived. What a disappointment for £60. I doubt it cost more than a couple of quid to make from polyester and nylon and the seams look narrow and feeble. I am working on my own “base layer” product specifically for track and road riders and would hope to produce a much finer product for £60. Packaging was the most impressive Zero Fit element.
In case anyone is interested I’m selling a Macna dry cooling vest https://www.ducatiforum.co.uk/threads/macna-dry-cooling-vest.106174/
Partner bought me a ZeroFit Ice Skin top for my birthday. Had it on trip to Ireland last week. Thought before departure it would stay in my luggage and my Helvarsons Merino top would be the base layer of choice. Whilst it was a degree or two cooler than the UK to combo of the ZeroFit and my Klim Marrakesh jacket did keep me pretty cool. Quite a bit of that being the airflow of the Klim I reckon. It's pretty thin but survived the trip. It feels very synthetic and a bit sweaty when stationary but did its job and was comfortable all day on the bike. Looked a bit of gimp at lunch and coffee stops though. I'd give it a score of 3 out of 5.
