Really top notch stuff and the owner is a really good guy. We've been dealing with them from almost their beginning, and have nothing but great experiences and a lot of happy Elzetta customers.
I have installed a ZHF1500 before. It was a little tricky as they give you just enough screw length to just get the thing on. So what's really helpful is get a clamp and clamp it to your rifle, then put the screws in.
Also, don't forget you can save 10% on Elzetta stuff with the ingo coupon code