Good used set of single channel pipettes. I will check accuracy after confirmed sale and make adjustments if needed using the gravimetric method. I have calibrated pipettes for over 29 years. I can send you a printout with each pipette tested. Also I will replace seals, o-rings or shafts if they appear to be worn. If you need it shipped quickly please let me know and will try to get it checked and shipped sooner. Pipettes may have markings or scratches from previous owners. This will not affect accuracy. You should have these pipettes checked by your own service provider if you require traceable documentation. Thanks