I had one of their TTX upper ball joints on the old Sierra. 'Had', because the UCA's mounting surface for the ball joint was so worn, the TTX joint literally fell out of it (!) during the 20min it took me to drive to the local school lot and break in my new pads / rotors . And I didn't notice it until a day or so later, when I was looking at it in my driveway. Scary.
The ball joint was ruined, but since new control arms traditionally come with new ball joints, wasn't a tremendous loss (went with Moog at retail, since I needed it all immediate-like).
I did like the TTX boot (thick, green, & had a protective cover over it, in the box) and the (2) zerk fittings had a little rubber cover (also green). Cute, I suppose.
The cotter pin for the castle nut was a weird affair - a reusable one that clipped in / out of place. Since the boot was compromised, I looked at the innards, once I got the UCA replaced. It looked to be a substantial piece, as one would expect.
IIRC, some website that had a lot of lifted truck owners were sourcing these TTX joints & selling them on their site (but not as 'branded' Mevotech). Seemed to be very popular with the ppl who bought them.