Heavy duty 5mm thick version of 3.5mm thick
NAM3760 as fitted from 1991 on but interchangeable with earlier
NAM3760 as an upgrade.
If you are upgrading in thickness check your fixing bolts/studs are long enough as this is nearly twice as thick. 1275 models from 1990 should have bolts which are long enough as this was fitted as standard but for earlier cars two longer studs
CHS2514 should be used.