Kedu ka esi egwu olulu a na efere MS & SS? Anyị nwere nzọụkwụ atọ, anyị na -ahọrọ mpempe mkpọpu mmiri atọ iji gwuo efere ahụ, nke kachasị nwere ike ịbụ ọkpụrụkpụ 20mm. Dịka ọmụmaatụ, mgbe anyị na -egwu otu efere nwere ọkpụrụkpụ 20mm, nke mbụ anyị na -eji ntakịrị mkpọpu ala iji gwuo omimi nke 18mm, wee jiri obere ihe na -egwu ala wee gwuo efere 2mm ikpeazụ, n'ikpeazụ jiri ntakịrị mkpọpu ala mee ka oghere dị elu buru ibu ruo omimi nke 10mm. N'ezie ọkpụrụkpụ efere dabere na ihe ndị ahịa chọrọ, anyị na -eji mbubata mbubata mbubata, nke enwere ike ịhụ na ahịa china adịkarịghị, ọ bụ ya mere anyị nwere ike iji mee oghere ndị conical maka ndị ahịa anyị.