Kalmar “tubu inch 3/4” gabaɗaya tana nufin diamita na waje (OD) na bututu.Don tantance diamita na ciki (ID), kuna buƙatar ƙarin bayani kamar kaurin bango.Ana iya ƙididdige diamita na ciki ta hanyar rage kaurin bango sau biyu daga diamita na waje.Ba shi yiwuwa a tantance ainihin diamita na cikin tubing 3/4 inch ba tare da sanin kaurin bango ba.