... very abrasive Hemispherical buttonl Universal buttonl Wearing resistance l Best suitable for hard rockl 25,000-45,000 PSI (170-300 Mpa ... )l Abrasive to very abrasive Parabolic buttonl Universal button l Fast penetration l Best ... suitable for medium to hard rockl 15,000-25,000 PSI (100-170 Mpa)l Mildly abrasive ground Conical buttonl Fast penetration ...