Fyfe and Parnell2 reported that only 5 of 18 transducers met then-current Australian Standard Specifications and International Electrotechnical Commission (IEC)4 recommended tolerance (±15%) of expected power, and only 4 of the 18 were within the tolerance level (±10%) for ERA. More recently, we5 examined ERA, total power levels, and SAI from a small (n = 7) cohort of transducers from a single manufacturer. Using calibrated transducers at 3.3 MHz, we reported that, although ERA and power values were within FDA guidelines, the SAI values varied from the digital display by −16% to +25%.5 To compound this problem, several researchers have examined the calibrations and power levels of ultrasound machines being used in clinical practice and reported large deviations in the power levels, which they attributed to poor calibration.6–11 Therefore, the purpose of our study was to examine 11 transducers from 6 manufacturers (n = 66 transducers) to determine the level of variability in ERA, power, and SAI for both intramanufacturer and intermanufacturer comparisons. These data may add perspective to the discrepancies in tissue heating that have been previously reported