75% humidity calibration standard for verifying and calibrating the same family of REED humidity meters (R6001, SD-3007, 8706, R6200, R9900, R9905, R6050SD). Also rated to roughly +/-1% accuracy at 77F (25C) and sized for probes up to 0.6 in (15mm) in diameter, complementing the 33% standard for two-point calibration checks.