Ili ndi bokosi lapamwamba kwambiri la mpweya, lomwe lili ndi zinthu ziwiri zapadera: 1. Chophimbacho chimakhala ndi kalembedwe ka gasket, ndipo gulu lapamwamba likhoza kupangidwa ndi pulasitiki, zikopa, diamondi, kapena mapepala apamwamba a quicksand; 2. Mankhwalawa amapangidwa ndi bwalo lapakati, lomwe limapangitsa kuti likhale losanjikiza komanso lapamwamba.