This is the copper based lubricant that comes with all Flexifoil stainless buggies.  Without it, the stainless-to-stainless hardware assemblies can seize together, a process known as galling.  (This is why Flexi and Peter Lynn rear axle bolts are not stainless.) Simply smear a thin film of the grease on threaded stainless steel parts before assembly.

If you bought a buggy used and did not get a tube of it, or if you are replacing non-stainless hardware with new stainless parts, get this stuff.  It is cheap insurance to keep you from having to reach for a hacksaw or blowtorch just to take apart your buggy. 

A small 5 gram tube (about 3" long) will last a while.