A great warmer is hard to find. But here they are: Starting with the fabric, Roubaix Plus, stretches amply while also providing enough compression so that they don't wander.
Next the tailoring. Arm warmers are long enough to avoid the dreaded arm gap above the tricep while at the same time covering all the way down the arm to avoid the wrist gap. A 2" laser-cut upper arm band with silicone gripper ink provides no slip comfort all ride long.