General Specifications for NRG COMPANY, INCORPORATED Rectangular Clarification Equipment Part 2 - Products 2.3 Wear Shoes   Flight wearing shoes shall be 1/2" thick Ultra High Molecular Weight (UHMW) Polyethylene material with a minimum molecular weight of 4.5 million, maximum coefficient of friction of 0.11 (UHMW on UHMW), and maximum relative abrasion resistance of 15. The wear shoes shall be reversible, providing two usable surfaces. To avoid the drilling of unnecessary holes, the floor wear shoes shall be attached central to the chain attachment link. Return wear shoes shall be equipped with guide lugs to center the flights between the return rails. Wear shoes shall include mounting holes to accommodate 3/8" diameter hardware.