Okay, so I read this and a couple other big brake threads on this forum since I will be looking for a set in the next few months and here is what I've gone through/found out. I called a few big brake vendors, including Hennessey, which sells a 15" 6-piston Brembo kit for the Raptor for $4750, and they also sell a 16" 6-piston Willwood kit for the F-150 4x4 for just over $3200. Now, what I wanted to figure out is why isn't the Willwood kit listed as an option for the Raptor, since it's obviously an F-150. So, I called up Hennessey, and the sales associate told me the reason the Willwood kit won't fit the Raptor is the hubs on the Raptor and F-150 with a 4x4 setup are different, but he couldn't tell me how or why they are different. I was not sastisfied with this answer, so I called Ford Racing in hopes of getting ahold of the SVT guys to see if they could tell me the difference. Ford Racing has no idea whatsoever. Next, I called a local Ford parts department back in the States and asked the nice Ford tech if the part numbers for the F-150 4x4 and Raptor hubs were different. According to the parts catalogue, they are different, but again, he couldn't tell me if this was because of a difference in vehicles or actual physical differences. So, I went to my go-to-guys, Team JDM, and the nice young lady on the phone was able to get the answer for me in about 15 minutes from Team JDM's go-to-guy for parts (a local Ford dealer across the street, I believe). The final answer is yes, they are physically different. They have different knuckles and mountings or something like that. I'm not technically inclined, so it was more gibberish to me, but it was more specific than "yes, they are different, no, I don't know why," so, I was happy with that. So, the conclusions for this whole exercise are: a. the Willwood F-150 big brake kit will not fit the Raptor b. there is an alternative to the Brembos from Baer Brakes who sell a 15" 6-piston front big brake kit that is Raptor specific for just under $3200. Bill at Baer brakes assured me they have installed a few kits on Raptors already. c. Stoptech does not make a kit for the F-150 or the Raptor d. the brakes from SDHQ are just upgraded 14" rotors (same size as the stock Raptor rotors but SDHQ's are slotted and/or drilled) and pads. SDHQ also seems to be the only vendor selling upgraded parts for the rear brakes (slotted/drilled/pads/etc.), as Brembo and Baer are only making front brake parts for the Raptor. I hope this helps anyone looking for their next upgrade.