I'ld have to pop the cover and pull them to know for sure. Their W 30gb for parity and 20gb for data just to test out.
Here's what the GUI show them as;
Model/Serial No. Temperature Size Free Reads Writes Errors
parity WDC WD300BB-00AUA1/WD-WMA6W1238303 * 29,316,640 - 2,234,937 2,238,511 0
disk1 WDC WD200BB-00CLB0/WD-WMAAR1325483 * 19,551,136 8,887,892 1,745,783 1,725,232 0
disk2 WDC WD200BB-00CFC0/WD-WMA9L1213864 * 19,551,136 5,479,884 1,600,727 513,279 0