In most cases the ID of the spring perch perch will match the thread size. The notable exception is on stock replacement struts such as the Koni Sport (Koni Yellow). These have a slightly larger diameter section below the threads. The data that I have been able to gather over the years is summarized below. Blanks indicate items for which I do not have confirmed data. Any information that you can provide to help expand or complete this table is greatly appreciated.

The plates are machined from 6061-T6 aluminum and anodized flat black. The spherical bearings are made-in-the-USA FK pieces rated at over 7000lb axial load. Shoulder nuts to adapt the spherical bearing to the thread on the top of your strut shaft are included beginning in September 2017.

The front mounts will move the strut top inward significantly farther than any other on the market, as well as providing increased caster (about 7.2 degrees on my setup). In the "standard" configuration they position the adjuster knob on your strut in line with one of the bolt holes in the chassis, enabling these camber and caster gains without requiring any cutting of the chassis, as shown in the pictures below.

These are not "camber plates" in the traditional sense, that is, they are not adjustable. My opinion is that the proper use of adjustable camber plates is to set them to their max camber position, and then use crash bolts to set the desired camber at the hub. The reason for this is that leaning the strut inward provides significant improvement in camber curves, as discussed in my suspension analysis, as well as gaining clearance for wider wheels and tires. Additionally, changing camber plate settings has a large affect on toe, making it a more complex adjustment than it would appear. Better to just set it up once, and set it up right.

The increased caster causes the wheels to gain camber due to steering input giving you more camber when you need it most. The end result of all of this is that you can get the same or better cornering performance while actually running LESS static camber, providing better braking and acceleration grip, as well as better tire wear.

A few things to be aware of regarding the use of these mounts:

1. They provide a LOT of camber in front. Depending on your ride height and how much camber you want you may need to substitute a smaller bolt for your upper crash bolt. I have used a 12mm Grade 10.9 bolt from the hardware store, which enabled me to get down to about -2°. Two of the smallest Toyota crash bolts will get you to about -3°. Other aftermarket lobed camber bolts may be able to achieve similar results to the 12mm bolt I used, although I have not tested to confirm this.

2. The increased caster does effect steering effort. Its not a big deal with power steering, but if you have manual steering it may be more than you want to deal with. The added caster also may cause tire rubbing on the rear inside edge of the wheel well at full steering lock. This can usually be resolved by adjusting the strut rod to pull the wheel forward in the wheel well. Aftermarket adjustable strut rods are required on a 93+ MR2 in order to do this.

3. Because of moving the rear strut top in, the rear strut may contact the frame rails at full droop on some longer stroke coilovers. This isn't an issue under any normal circumstances, but it does limit droop travel slightly. Just something to be aware of. You may need to lift the hub with a jack and slightly compress the strut during installation. Most coilovers have a short enough stroke that this does not occur.

4. These mounts REQUIRE the use of a separate upper spring perch. Unlike many rear mounts, they are not designed to be use as a combined strut mount and spring perch. If your coilovers do not have a separate upper spring perch in the rear you will need to purchase those as well.

5. Due to the large diameter of stock and stock-style "lowering springs", these mounts will not work with those setups. Sorry, coilovers only.