He mentions caliper not drums which do use cylinders. Early Astras were fitted with Bosch calipers, these were replaced around 2001 with Lucas calipers which are far superior. The Bosch has ridges on the upper surface, the Lucas has a smooth upper surface. None of the calipers are repairable as there are no kits available, best bet is to source a set of Lucas calipers which are a straight swap for the Bosch ones. Don't try the newer MK5 Lucas calipers as they look identical but won't fit due to a different caliper carrier being used with a lower offset.
Oddjob, September 2008
