I have more than one pair of these, and they do keep your hands warm as glove liners. They're also thin enough to go inside protective work gloves and even heavy skiing gloves - I haven't found a glove they won't fit inside yet.
Now for the bad part. Roughly one in two of these gloves have poor quality fabric where some of the elastane fibres haven't been woven in properly, which means that they create loops for your fingers to catch in as you put the gloves on. It's remarkably annoying.
I just cut the loops with a pair of scissors and left it at that, but it doesn't inspire confidence, and it shouldn't happen with a product costing almost £10 a pair. That's why I've only given them an "average" / 3-star rating - they do the job, but quality needs to be more consistent.