Disclaimer, I am not associated with Hatfield’s Gunsmithing, other than being a customer. This is a new product I discovered at my local gunsmith shop, Hatfield’s, in Manassas, Virginia. I thought this was a cool unit for its intended purpose. Sam Hatfield, the owner and former armorer for the AMU, designed and built these units to assist with one-handed operations of the Glock slide, and more. From what I understand, he will be soon coming out with one for the M&P – which was specifically requested by one of his customers who has use of only one arm. Other than one-handed operations, the Hatfield's Racker, can help with expedient operation of the slide…slingshot, malfunction clearing, etc… Installation is quick and easy. Simply remove the existing slide plate cover, and replace with the Racker. About 5 seconds, and you’re done. As you can see, the internal shape of the Racker matches that of the original slide plate. I have done many dry-fire exercises with the Racker, but have not been to the range with it, yet. Use of the Racker in place of your rear sights for slide manipulations on pants, belt, etc... is quite a bit easier. You have no chance of missing your garment, or having it slip. There is some definite positive contact. One of the side motivations for the Racker, according to Sam, is to assist female shooters with operating the slide. With the potential of weaker grip-strength, the Racker gives a bit more purchase for easy operation. Additionally, if you have a slippery residue on your slide, or if you are wearing gloves, the Racker can assist with that, especially under stress. Personally, I can see the benefits of using this unit, for the above listed reasons…primarily, one-handed operations of the slide. However, there are some challenges. Primarily with conceal carry. The Racker will add about ¼ inch to the profile of the rear of your slide. In winter, no worries. In summer, with only a t-shirt on, maybe. But, maybe not. I think it will depend on the body type and how you carry. For “combat” carry, I can defiantly see the advantages. Once I get out for some range time later this week, I will post a live fire update. Overall, a nice little addition to your Glock, and soon your M&P.