My trailer has a circuit breaker between the batteries and the wire that goes into the trailer.  It is worn and falling apart...it needs changed.  It looks like this:

http://www.wiringproducts.com/contents/en-us/d60.html

The writing is worn off so I can't tell what size it is (ie 20 amp, 30 amp), what size should I replace it with?

Mike

Just look at the wire and you determine the breaker needed. 

10g = 30 amp

12g = 20 amp

14g = 15 amp