Blind joint threads are a bit rough but functional. Not a single hole in the extrusion faces was drilled to spec blind joint holes at the ends of the B extrusions were off by ~1.5mm, Y axis mounting holes were off by ~2.5mm, center hole in C extrusion was off by ~3mm, etc. Extrusions are reasonably straight, however machining is way sub par: out of all extrusions in the kit, only one (!) was cut to the specified length all others were 0.5-0.7mm longer.