What do you guys think about these ? maybe help keep a shaft from twisting ? BBB

never seen it before maybe to convert a bravo to accept xz/xr prop

Yes that is what I think, but will it make a stock shaft less prone to twisting, ? Notice it's fully splined in and out. BBB

would think the opposite less material....like the outer shaft on a bravo 3

A bravo 3 outer shaft isn't splined on the inside. Every Bravo/Trs/ Alpha that I have with a twisted prop shaft is in the spline area. Usually in the middle of the splines. Very rare on alpha it usually blows the pinion gear first. I would think that putting this between the prop and shaft also using the XZ solid Flotorque adapter would substantialy reinforce the shaft. Unless there is a fully splined adapter or prop hub that would fully distribute the load on the propshaft. Just my 2cts. BBB

who makes them?

Even if it does keep the prop shift from twisting, I think all that will probably happen is the lower vertical shaft splines will twist instead.