Bought these for temps in the 40s but they don't work well for me when it's that low. They do work well in the 50s (for me). -I do have cold hands so take my opinion FWIW.
The issue is the design. It has some noticeable insulation on the back which works but nothing on the palm side. I am sure that sounded good at the design meeting but....ever hold cold bars? Yeah, it comes right through. Duh!
Finally, cold weather arrived and a true test for the Pearle iZumi AmFBI gloves. To coin the phrase, "fits like a glove", easy on/off and kept my hands warm. The gloves are light and have a comfortable feel on the hand. Able to use to the Garmin as well as the phone while wearing the gloves. The materials to construct the gloves are of quality, no complaints. They are replacing an old pair of Pearl Izumi gloves that have lasted five years.
I have Raynaud's syndrome (cold hands). I bought these as an outer layer for my electric gloves. They don't work well for that purpose. They might work okay for other purposes.