I-GB Standard Round Barluhlobo lwentonga yentsimbi eyenziwe ngentsimbi ye-carbon, eyi-alloy yentsimbi kunye nekhabhoni. Imivalo yentsimbi yekhabhoni ifumaneka kwiimilo kunye nobukhulu obahlukeneyo, njengokungqukuva, isikwere, isicaba, kunye ne-hexagonal, kwaye ziqhele ukusetyenziswa ekwakhiweni, kwimveliso nakwimizi-mveliso. Le mivalo inamandla okuxinana okuphezulu kwaye iyaziwa ngokuhlala kwayo kunye nokuchasana nokubola, izenza zilungele iinjongo ezahlukeneyo zesakhiwo kunye noomatshini.