Dakota NDT T-700-4405 10 MHz, 1/8in Diameter, Single Element Contact Transducer, Standard. Dakota Ultrasonics single element contact transducers are for use with Mini-Max bolt tension monitors. These transducers are available in magnetic or non-magnetic versions with both versions suitable for fasteners of all metal types. Available sizes include 1/8, 1/4, 3/8, 1/2 and 3/4" diameters. The transducer is also available in 2.25, 5 or 10 MHz versions.