Waygate Technologies Krautkramer ALPHA DFR-P [113-118-661] Plastics Delay Line Probe 20 MHz x 0.3 Inch Contact Dia. The Waygate Technologies Krautkramer Alpha DFR-P Plastics Delay Line Probe, a Baker Hughes business product (formerly GE Inspection Technologies), has a frequency of 20 MHz and a 0.3" contact diameter.  This probe requires the C-604 probe cable.