He ʻāpana hakahaka ka paipu kila a ʻoi aku ka nui o kona lōʻihi ma mua o ke anawaena a i ʻole ke anapuni o ke kila. E like me ke ʻano o ka ʻāpana, ua māhele ʻia i loko o ka pōʻai, square, rectangular a me nā paipu kila kūikawā; E like me ka mea, ua maheleia i kalapona structural kila paipu, haʻahaʻa alloy structural kila paipu, alloy kila paipu a composite kila paipu.