The mantis v drive is very expensive and probably one of the worst designs I've ever seen.I went through two sights and one sight head before I finally gave up on it and sent it back for good.TR customer service was very good but the sight was terrible.It was heavy and the yardage marking were hard to see because they put them on the side of the sight instead of the back.The worst thing about it was the noise.I would never keep something that loud on my bow.Remember I went through two sights and an extra sight head so this isn't an isolated incident.Do a search on them.The results have not been positive.