The cause of poor loading performance from the CPC 464 is often a perishing drive belt becoming slack, or more commonly kinked where it has sat without moving around the drive pulley for 30 years or so. This kink then becomes a permanent feature of the belt causing it to jump and slip.
The tape counter belts don't usually snap or degrade to the same extent as the main belt, but can slacken off over time and start to slip.
These square section belts are newly made and are as close as possible to the size to the originals, but made from modern, more resilient materials. They have been tested extensively with the CPC 464 and work perfectly.
Please note - these belts ARE NOT suitable for the CPC 464 Plus model.