As detailed in the SU-16 and PLR-16 forums, these are the PLR version parts that will also fit both SU-22 and PLR-22, as well as SU-16D models. These are early parts with some hand deburring that has been mechanized since, for production, as well as a fixture related accuracy issue with the position of the holes in the front used for mounting extensions. These holes are off horizontally as much as .01 inches in these parts. The bolt holes are oversized enough that this does not affect their utility, but the 1/8 dowel pin holes used for automatic precision alignment will not be useful. No matter, it's easy enough to just align it by hand before you tighten the bolts, and just leave out the dowel pins (saves weight anyway). Other than that, these are good parts that are completely identical to the final production models, and you can have them sooner, for less. $100 each. I have five available. Final production parts will not be available for another couple weeks or so, and will cost $130.