Our turnbuckle style lowering links are infinitely adjustable between stock height and a 4 inch drop.  No need to remove bolts and disassemble the rear suspension everytime you raise or lower your bike!  Just loosen the two nuts and rotate the center hex.   The body is gold zinc plated steel or stainless steel.  The ends have a 1/2" thread and are black oxided steel. Aluminum threads DO NOT last and are dangerous!  We manufacture, assemble, market and sell these links...thats why we offer them at such a great price!