I've just been on the phone to my man at Gloucester Road Gearboxes in Bristol and the Vectra B from 2000-2002 as a normal Single Mass Clutch. The Vectra C from 2002 onwards has a Dual Mass Clutch which is a completely different assembly.
Here is an exploded view of a Daul Mass Flywheel.
The following is from the LUK website.
DUAL-MASS FLYWHEELS
The dual-mass flywheels absorb engine vibrations before they are transmitted to the driveline where they can create gear rattle. The unit is split into two sections: a primary section that bolts to the crankshaft, and a secondary section, onto which the clutch is bolted. The primary section dampens, isolates engine vibrations and prevents engine torque spikes from damaging the transmission. By design, dual-mass flywheels cannot be resurfaced.
SOLID FLYWHEEL REPLACMENTS
LuK engineers have developed solid flywheel replacements from some OE dual-mass applications. Designed as bolt-in replacements, LuK RepSets and solid flywheel options provide increased torque capacity and many feature clutches with a larger diameter than the original clutch they replace.
http://www.lukclutch.com/products/flywheels.phtml
