Well, I got the medium neck roll. I am between sizes on the chart at the website for tempur pedic. 5 9 1/2 and the cut off is 5'9" or 5"10" wife measured me at 6.5" neck to shoulder. So I have the 4 inch neck roll. Laid down with it and wife says neck is level. She has a Kohls brand and has had it a year. Less dense foam and so now that it has broken down, really soft compared to the TP. My neck feels great on it, but then after 5 mins, I notice that my head is higher than my neck, which means there is less support under the neck. I can also sleep face forward with her pillow. Guy at Bed Bath and Beyond told me that I could use the small side and turn it sideways a bit and use that for the belly and that aint bad. I think I prefer that than having my head elevated a bit and since the small part of the neck roll is thin, well, that is like the bunched up down. I will not be so quick to take this one back, and will give it a week.
By the way, go to the Bed Bath website and sign up and get 20% off - just so you can save some money.