quite a few models across the VAG range use a similar style of caliper to the MK2. if they're alloy they're MK4 type, if not they're MK2/3 type. if theres a massive spring on the handbrake mech they're mk2, but if from audi a3 they're more likely to be MK3/MK4 stylee.
edit: there is also a conversion you can do using late SEAT/Polo parts, to the later type of rears that use a seperate hub & bearing rather than a rear disc with a built in bearing. Pics with the wheel off will help
