Purchased this back protector to replace a Knox Aegis 8 plate protector, I ordered a size large and length wise it is very similar to the 8 plate which is what I was looking for. This is by far the most comfortable protector I have ever worn, it does seem to disappear while riding the bike and the temperature sensitive foam really does make a difference in how the protector conforms to your body and movement. Now, there is one thing that I do have an issue with which is minor but worth noting. Where the straps connect at the top you can see in the pictures that there are two little padded wings that extend off the back protector. It seems as if they have slightly changed this design on the later models as compared to what is pictured and the lower part of the flap is a very flexible foam covered in cloth that for me catches on the neck of my suit when I try to put it on and requires that I do some serious reaching or ask for help from someone to unlatch the flaps from the neck of the suit so I can get it over the back protector. I am still giving this 5 stars because once its on it is fantastic but I do want to at least make it known that this is an issue I have experienced which is a minor annoyance when first suiting up for the day and would be worse if you like to get out of your suit between races (I generally do not).