When i was looking i was torn between the 511, GPS and the DDA packs. I researched them all and even seen the 511 and GPS on the range. I ended up going the DDA route. Ill be honest it is one of my favorite purchases i made. I went with the medium because the large was just so big. I will say this, had i went with another one and then seen the DDA on the range i would have immediately sold whatever i had to buy the DDA. the quality of the stitching, material and the compartments are truly on a different level.