Si loo go'aamiyo dhumucda derbiga ee tuubada 3/16, waxaan u baahanahay inaan ogaano dhexroorka dibadda (OD) iyo dhexroorka gudaha (ID) ee tuubada. Haddii dhexroorka dibadda uu yahay 3/16" oo aan macluumaad gaar ah laga bixin dhexroorka gudaha, si sax ah uma xisaabin karno dhumucda derbiga. Dhumucda derbigu way kala duwanaan kartaa iyadoo ku xiran nooca gaarka ah ee tuubooyinka iyo heerarka wax soo saarka.