Anet A2 Z axis upgrades

Those parts will reduce flex of A2 Z-axis and therefore reduce Z sagging, which causes first layers to be crushed on top of each other, a lot of extruder clicking, elephant foot and prints being several tenths of mm lower than they should be. In standard form my A2 produced prints that were 0.6-0.7mm lower than designed, all due to Z sag and flex. Those parts eliminate most of it, my prints are now less than 0.1 off. The stabilizer actually contributes more, so if you want to have a quick win, just use the stabilizer.
Picture shows older version of the motor mount which, as I later discovered, limits Z travel ~12mm, so the STL has a cutout in the bottom part for the wheel (black marker on the photos).

UPDATE: I have now switched to inverted Z http://www.thingiverse.com/thing:2199187, and like it even more than this thing. Even though it's created for dual lead screws, I'm currently using it with single stock one, waiting for my parts to arrive. 100% Z sag eliminated. It is a bit more difficult to align due to short distance between motor and Z nut at Z=0 height, but once it's sorted, it's excellent.
If you are a fresh A2 owner just starting up, I suggest just printing the small stabilizer part from this thing here and using it to print the inverted Z parts.