Henry ya done well my friend, dropzone is the older model and you want the varizone. What it does is, sight in at 20 fer speed of yer arrow. Then check it at 30 to make sure its on the money. If not you adjust it at 30 and it should be in there fer 40 and 50. Spect awshucks can add abit more to what we have told ya. If ya like a scope on a CB its the cats meow. Talking of cats and meows, that will put squirrels fur on end, they don't get along none to well! hehehe.