Thanks for the great write-up, @REI-JohnJ - I just bought the REI liners and they were great the first time I used them. In addition to adding thermal protection, they're also moisture wicking. When I hike, I try to keep a brisk pace so I sweat and having those gloves pull the sweat off of my hands goes a long way to keeping them safe and warm.
So, to add to the original question - no, they don't add any noticeable bulkiness to my gloves and I use a pair of gloves I had before I ever bought the liners. And, @KFridman , I'd also say make sure your liners will be moisture wicking, too.
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