This is a Seal 60 x 72 x 8 Viton Single Lip for a National vacuum challenger 607 pump. This part fits all National Vacuum 607 PRO Challenger Series vacuum pumps.
This is diagram part #9 on the 607 PRO fan cooled pump exploded view and diagram part #9 on the 607 PRO liquid cooled pump exploded view.
The National Vacuum Equipment Part Number is 120-018-367