Cov hlau sib dhos ua ke ntawm cov hlau hloov pauv, xws li} mm, tuaj yeem siv rau hauv cov tshuab sib xyaw, xws li Shafts hauv cov tshuab yooj yim {{8} Loj - txoj kab uas hla sib xyaw ua ke, ntau dua 100 hli, siv rau cov phiaj xwm hnyav - ntsuas khoom siv thiab cov khoom siv hnyav -.