Instead of iron flat washers, we used bowl-shaped copper washers to effectively protect the O-ring and make the mixing ratio screw easier to install. The use of fluoroelastomer O-rings instead of silicone O-rings or Dingqing has the advantagesof high temperature resistance, oil resistance, and aging resistance. Mixture screws (early & late). The item "Weber 40IDF 44IDF 48IDF Carburetor Repair Rebuild Kit Improved kit brass screw" is in sale since Tuesday, November 27, 2018.This item is in the category "eBay Motors\Parts & Accessories\Car & Truck Parts\Air Intake & Fuel Delivery\Carburetor Parts". The seller is "henkyo" and is located in Hong Kong. This item can be shipped worldwide.