Ko te whanau poroi porohita o waho he momo rerekee o te riipene porowhita hohonu, e tohuhia ana e te mata porohita o te diameter o waho o te mowhiti o waho, a ka taea te whakarite ki te porowhita concave e rite ana o te nohoanga e mau ana ki te mahi whakahāngai.Kei te nuinga whakamahia te kawe porowhita waho ki te mau i te radial me axial kawenga whakakotahi i runga i te kawenga radial, a ko te tikanga e kore e pai ki te kawe i te kawenga axial anake.