Dramatically improved probing accuracy achieved testing high density fine pitch boards that were not testable with the standard model. E4H6151 corresponds to testing standard sized board with up to min. pad size of 20µm and min. pad pitch of 50µm. Whereas E4H3325 is specifically designed for testing high density general module and mother boards with up to min. pad size of 15µm and min. pad pitch of 45µm.