F-5 Injection Systems. We are proud to offer our pattented F-5 Injection System. Our professional windshield repair kit comes with a 30-day money back guarentee. Try it out! If your not fully satisfied with our injection system simply return the kit within 30 days for a full refund. All you would need to do is pay to have it shipped back to us. The F-5 is the BEST injector on the market. Our injector is faster, cleaner, and very easy to use. It also has no clean up so turn around time is cut in half. When is comes to most injectors on the market, they consist of 1-2, possibly 3 parts. That means if you were to break the injector, you will more than likely be out of pocket a few hundred dollars replacing the whole injector instead of the 1 broken piece.