Fox bump stops control the last few inches of compression travel up front. The forces that go through the bumpstops required the strength of a tie bar between the shock and bumpstop mounting hoops. Note that the bumpstops contact strike pads on the top of the upper knuckle bolt. If you use hydraulic bumpstops with this T.C. kit you'll need to do the same, as the lower control arms are designed to be used with stock-style bumpstops only.