You can run orals at the end if you haven't used it thus far, I've done it once or twice before. You may wish to run aromasin if you're near the end, thats one AI you can actually overlap with PCT. But arimidex is fine als, usually 0.5mg EOD will suffice for anything below 40mg with dbol, unless you're sensitive (then kick it up to 0.5mg daily).