I bought these for snow yet to fall so cannot comment fairly on their effectiveness though they seem and feel substantial and of a reasonable quality. This review is for advice on sizing and a comment on my customer experience.I bought my normal size UK 9 but because of the thickness of the detachable thermal inner lining discovered I needed a size larger. I returned them and promptly received a pair of UK size 10 which in my normal socks fit fine. If you will be wearing thick hiking socks or extra layers you might consider going up 2 sizes.Do not make my mistake and buy your normal size. Purchases via Amazon Market Place are returned at your expense. It cost me £13 plus to return these boots by Royal Mail and I was requested to contribute a further £2 towards the suppliers costs. As I said earlier, the very substantial thermal lining means you WILL require a size higher in normal sock-wear.The boots came well packed and promptly and the replacements also.The supplier handled my purchase and return promptly and courteously though I was dismayed by the aforementioned £2 returns levy. In hindsight, I don't think I'll buy footwear on-line again. I believe footwear, indeed clothing in general, needs to be tried on to ensure fit and comfort.theloxleycountryclub cannot recommend buying footwear on-line because of the sizing issues and because of the costs of any returns or replacement issues caused by the above.I normally wear size 41.5 or 42, but ordered size 43 to allow for thicker socks, but the size 43 still didn't fit me wearing normal socks. I ended up having to pay £6.19 to return the boots. There is clearly a sizing issue with the boots as confirmed by two other reviewers, but the seller won't accept this, causing significant cost to the hapless buyer. Also, I bought these boots to go to northern China where it will be -30C, so these seemed suitable given a -40C comfort rating. Another reviewer says they are only good to -5C and certainly one's feet don't feel warm right away as they do with many other extreme cold boots that I have now tried. These boots are also very heavy and bulky.better to have a left and a right foot inside to boots... I am still awaiting refund and different inner for left foot