The adapter is so the button fits the top of the handle, you need the WRX one to ensure a good fit up. I had to take a little material out of mine to get the button to move freely but it was easy with some sandpaper(wrap it around a pen or marker).
The e-brake is pretty easy to install. You need a boot if you want it to look nice. I had the polished momo in my wagon and now it's in my STI, same install, very easy.
1. Remove center console around brake.
2. Drink Beer.
2. Cut old brake handle cover off(it's rubber and glued on - cut it down the seam underneath, very easy and you can reinstall it if you really wanted to).
3. Drink Beer
4. Install(I had to sand where the button goes thru the handle so it moved freely).
It's super easy should take a few minutes even with beeer breaks. Center console just pops off, pull gently.
This is a mess... I have read all of the installations, and they are all really bad. No offense. I'd like to help by offerring a solution to the bad alignment, poor boot fitment, and a couple of things that will assist in allowing smooth button release and ratchet system function to be retained, if not improved during this installation.
There are two options for Momo brake handles, and both use identical mounting hardware, and require the same supplemental parts to install correctly. These consist of the tube style and grip style. The Pit Stop (the one I've got) is the one I will show install pics with. Rest assured, if you have a machined piece, it will fit the same way, and the same issues must be resolved to align the handle and button.
I am also using the A2/C2 combo for a button hole size. My method for correct alignment is to use a BMW brake button. This has a threaded hole which must be heat-welded to the Subaru brake button after some scuffing). With the elongated button(s) sanded smooth on the sides and filled w/ weld, the handle will slide on and stop gently on the button's shoulders. At this point, three medium length (7mm x 3mm) spreader screws on the sides and bottom of the handle, and one short (4mm x 3mm) spreader screw (these are the allen set screws provided), and a dab of epoxy on each screw should set the handle snug and solid within about 5 minutes. With the handle in place, it's time to install a boot.
Momo's boots work with their handles very nicely. There are a modicum of other available boots which will fit, but for the sake of ease it makes sense to just get a piece which you know is going to go in without a fight.
The least amount of material possible makes for the best installation. The exposed metal behind the handle is narrow, and does not provide a body to adhere a fitted boot to, so we must create one. Closed cell foam is great for solving this little problem, and with a few cuts w/ a hobby knife, you can easily carve a body to fit the metal tube. It only has to fit into the rubber boot-surround on the console, something I did away with, but could be kept if you prefer.
With the boot installed, there could be some binding on the rubber surround, so I removed mine, and used the pins to center my boot for more welding. I chose to use Sparco Classico Black Leather boots for my console. The stitching matches my seats, and the leather is identical to that of the Sparco wheel I am using, also red stitched black leather. Many Sparco products are made by Momo. Most of these parts are compatible. My boot fit my handle exactly as it did the Sparco handle which I was using previously.
Forming the foam and gluing it down was a little painful, but once done, I was glad to have taken the install so far... it fits like OEM, and works like it should. The base does not hit the console, and it fits centered between the shifter box bulge and the armrest box, when I touch the button gently it does not wiggle, and when I depress it, it releases and engages solidly.
I recommend relubrication of the system during this installation, the gears on the base get dirty over time, and this friction is only felt slightly... but it counts.
Here's a pic I made of what to cut, what to glue, and what screws you can use without cracking the VERY thin metal shell inside the handle cover:
This is what it's link in the down position. It fits like OEM, but it's a thousand times classier. Sparco Classico boots, Tungsten 2lb ARC knob, TWM short shifter, STi trim powdercoated, Bride seats...