Barton mainsheet traveler truck

[Nikki B]

Hi i need to replace the truck on my traveler as the end are worn and let all the balls fall out.
Apparently there are 4 sizes but i don't know how to tell what size it is.

 

[Egbod]

Replacement balls are available. You hold them in position with squirty shaving foam then when assembled use water to wash the foam away. Do not use ordinary grease for this.