Rear PTO seal kit includes aftermarket replacements for the RE13181/AT16431 seal, R33337 gasket and P50631 o-ring all of which are usually required to replace the rear PTO seal on the following tractors with 540/1000 PTO. 2520, late style 3020 (above s/n 123,000), late style 4020 (above 201,000), 4030, 4040, 4050, 4230, 4240, 4250, 4320, 4430, 4440, 4450.