Replacement tire valve for road graders & tractor tubes. Base prepared for electric or chemical application to tubes. Road grader and tractor valve replacement TR 218A Base is 4 1/4", valve 1 27/32" Base for electric or chemical application Skincard 0. Replacement tire valve for road graders & tractor tubes. Base prepared for electric or chemical application to tubes. Road grader and tractor valve replacement TR 218A Base is 4 1/4", valve 1 27/32" Base for electric or chemical application Skin card 0.