I have been looking for something to replace my all cotton padded undershirt and Reebok nailed it. This shirt provides great collar bone and neck protection (and side protection if your C/A doesnt have a belly wrap). I stopped wearing a hanging neck guard several years ago and just dealt with the added heat of the cotton padded undershirt, but I no longer need to just 'deal with it'
I have stayed very cool while wearing the shirt, yet the added bulk of the padding isnt noticable. I was a bit nervous about the long sleeves, but they have aided in keeping my arms cool, plus my arms slide in and out of my C/A very easily, which is great for last minute adjustments.
With all wicking material, only air dry after washing, never in a heated dryer (it erodes the wicking attributes).
I wear a 15-15 1/2 shirt with a 42R chest and a large fits me perfectly...tight enough to stay in place, but not so tight I feel constricted.
Only negative is the price tag, but if you play once/week...one shirt is all you will need.