Sampling of the shells is done with the Merchantek EO MicroMillu. The MicroMillu is a computer-operated milling machine with a 50 mm wide drill bit. The milling path is set with the MEO MicroMillu computer program. The MicroMillu is therefore able to sample along the growth bands, taking out approximately 50-100 mm width of shell in each scan. With this method it is possible to get monthly resolution in the oxygen isotope record. By sampling across all of the growth bands it is possible to get a mean value for the lifetime of the shell.