oring

what is the thing circled called? im trying to buy a replacement oring. its a grundfos pump modle number: 10-40957-130008-1782P.

Manually vacuumed the pool into the skimmer. Our auto leaf vac is getting new tubes. Had a brain fart and lifted the vacuum out of the water. Air got sucked into our only intake/skimmer. I freaked out and ran to turn off the pump. Emptied pump basket. Waited a minute and turned it back on. Water...