The majority of Alnico magnets I have measured on “Patent Applied For” pickups have the same dimensions used in the older P-90’s that are often called “Soapbar” pickups. The general dimensions are 2.5″ long, .50″ wide and .125″ thick. The magnets are magnetized North and South across the .50″ dimension. The magnets are sand cast and at times surface ground to yield proper dimensions and tolerances.