This is a drop in replacement for the Y assembly rod holder that holds the X axis rods. I replaced 2 of the brass inserts with m3 nuts on the opposite (inner) side. You have to use 40-50mm m3 screws to reach across the part to the nut. The advantage is that you can now tighten the screws properly without pulling out the brass inserts. Since 2 of these are replaced in a diagonal position, the stability is much improved. The other 2 inserts could not be replaced, but they are not important. Tigthen them as usual so there is no gap between the Y axis assembly parts.