This kit was purpose-designed to fit a BobC holo projector with an adapter that screws into the back side of the HP, mounts an included 6-wire slip ring, and has a laser cut aluminum plate that adapts to the BobC HP ring mounts, and holds the two micro-servos used for positioning the HP.
The slip-ring adapter has a place to directly mount a REON HP board, and an option for acrylic adapters for the Filthy HP board.
There are two other kinds of HPs that have been made for R2 builders in the past. One by Jason (Pwrsrce) and one by Dave Shaw.
All three of them have a different thread at the back of the HP, so there are different versions to select.
BobC - This entire kit is made to fit the BobC HP. I have seen his mounting rings installed more than one way. You can see in the photo above how I mounted it and how the servo mount adapts to it.
Jason (Pwrsrce) - This has two different thread lengths on the back of the HP. There are two length options. Short and long. Both fit, but if you have short threads, the short version will look better when installed. The kit comes with the servo mount hardware, but that hardware specifically fits the BobC mount. You will likely have to come up with a way to mount the laser cut servo holder.
Dave Shaw - These HPs have pretty short threads, similar to the Pwrsrce short thread version. Like the Pwrsrce version, the kit comes with the servo mount hardware, but that hardware specifically fits the BobC mount. You will likely have to come up with a way to mount the laser cut servo holder.
Note: Servos shown for reference. They are not included.