The E-meter is a Wheatstone bridge measuring skin resistance; the preclear holds two cans and the auditor watches a needle. Sessions run to the hour and are logged; the auditor follows a fixed procedure and is trained and certified in it. Scientologists describe good auditing as the single most valuable thing they have bought, and the phrase is exact — the Bridge is priced service by service, and the total cost of the upper levels runs into six figures. That pricing is the criticism most often made from outside and the one the French fraud conviction turned on. The church answers that its members pay for training the way a university charges tuition.