The 800 Series fits the Model 1430 and Model 1530 Frames. They have 50 mm of calibration and are 6.3 mm square.

The 900 Series fits Model 900 Series Stereotaxic Frames. They have 35 mm of calibration and are 6.3 mm square.

The 1700 Series fits the Model 1730 Frame. They have 50 mm of calibration and are 9.4 mm square.

Please specify stereotaxic frame to be used to insure compatible ear bar series is quoted.