Photos of the Volas Vitality™ MagicPro 2.0 show inner padded contacts and rounded contacts on the upper arms.
Keep the open U even, pads inward, and the button panel reachable. The listing does not give a neck-circumference range. Do not bend the arms to invent a custom fit.
Look at the Volas Vitality MagicPro 2.0 images to see the contact layout.