I haven't tried them yet but here are a couple quotes from a different thread. This option may be just what you need...
Originally Posted by Justinb306
Just did the install. I was missing the 2 u nuts and 2 bolts to go with them. I couldn't find a metric u nut with the correct depth to match the others. Most metric u nut depths that match the OEM bolts are 19mm and you need roughly 28mm depth. I went with sae thread Napa Balkamp u nuts part #665-1961 package of 3 you only need 2 of them. They are 3/8 - 16 screw size and just picked up 2 sae 3/8 - 16 Grade 8 bolts and washers from them. I think the bolts were 1 1/4 length. You can go longer if they don't have the correct length.
A GM part number comes up for the u bolts that matches the Jeep OEM metric bolts with the correct depth. The number comes up in their computer but they said no longer available.
Dimensions : Panel Range - .05" - .2", Center Of Hole To Panel Edge - 1 1/8"
Manufacturer : Auto Fastener Group, Inc.
Manufacturer Part Number : 46029
Material Type : Steel
Mounting Hole Diameter : 3/8"-16
Package Quantity : (1) Nut
Style Name : Extruded U-Nut
Thread Size : 3/8"-16
As I roll down the trail,I hope my traction will not fail.But if I spin & begin to slide,please dear lord protect my ride
Are you sure? Notice how deep the required u-nuts are? The way I understand it, they aren't your standard u-nut that you can grab anywhere...
Well, I didn't take any out of the package to measure them, but it said it had the same measurements as the rock rail mounts I was looking for. I was only browsing at the time, but they looked just like what I had bought from www.clipsandfasteners.com.