This is for stiffening the X-Axis of your X-Carve (2015-to early 2017 models). Per pair, you need:

• m3 x 55-60 mm screw
• m3 thread insert
• 10-11 mm washer
• 14-15 mm washer

I recommend from 2 to 4 pairs to be placed on the rail.

Also check https://www.thingiverse.com/thing:4336323 for the Y axis