ERF6000 : Indexbal endmill with 20mm high posi-rake button insert for difficult-to-cut material
  DesignationStockAPMXDCDCXCICTDCONMSLSLFGICATGIREMgiic
  ERF6050R Available10.0050.0070.00332.00080.0120.006804360 0
  ERF6063R Available10.0063.0083.00432.00080.0120.006804361 0

These are not irregular pitch spec.