Review on Warm Winter Convertible Gloves: Flip Top Mittens for Texting, Photographing, and Running - Men and Women by Shane Tomko

My hands are still cold but as soon as they get warm they immediately start to sweat. I'm glad I chose size S (my arm circumference is 7.25 inches) as size M would be too loose for me. I love how I can snap off the tops when my fingers get hot or I need to use my phone. Narrower near my wrist so it doesn't fall off easily. The top of the thumb doesn't need to be opened, but I can confirm that these gloves have that feature too.