Jewelled Pivot Caliper Jewelled Pivot Caliper "Bradux" is brass sanded, chrome-plated with jewelled pivot protectors with a hole diameter of 0.15 mm. This is a top of the line caliper that permits complete visibility of the balance wheel collet to allow room for adjustment to be made to the hairspring of the balance wheel. The balance is free to be spun and corrected with spring arc. This is a Bergeon Swiss quality product.