We recommend that you use the Boveda Calibration Kit so that you can most accurately calibrate your hygrometer
While our packs are accurate in an airtight environment within +/- 1%, our calibration formula is even more accurate, within +/- .5% and is our recommend formula for calibration.
If you wanted to use another Boveda pack you could, but we do not recommend the 49% RH packs as this formula is designed to be a specific range of relative humidity instead of a specific relative humidity like our other packs.