There are three links for lowering the rear of the Kawasaki KLX250.
The KLX4 links lower the Kawasaki rear approximately 2" but are only for non-aggressive riders who require the maximum lowering.
Fits: Kawasaki 1994-up KLX250/300 and 06-up KLX250H6F Dual Sport. Note that these links will fit the '09 KLX250S/SF dual sport and Supermotard models, but lowers the rear 1/4" less than on the 06-08.
Yes they will fit the 2018.
As long as you understand how to set your SAG and follow up setting the bike up correctly they could work.