i'm thinking about getting a trracer on ebay or something to see if i like pump then moving to a phantom. i've read that some trracers don't have velocity adjustments. is there an easy way to tell if i'm getting one with the velocity adjustment? specifically if i'm just looking at a blurry picture on ebay. where is the velocity adjustment located on the trracers that have it? is it somewhere visible where i could see it? thanks!