The standard anchor roller wheels on the 400 Trawler are a hard nylon that wear and split in half in a short time. The best replacement for these is the Windline W50 or W40 Marithane wheels. Hand cast from an elastomer unmatched in ability to resist wear and distortion at high loads. More durable, yet quieter than either hard plastic or metal. Virtually Indestructible. W50 - Diameter: 5" Width: 3.4" Hole Size: .5" By Windline.
The best source I have found for these is Bosun Supply.