I have used two systems:
1st, I tried the Black Plastic cars with Murray's #01-3112. They worked great, but the line does not run as free through the plastic. My crew had trouble trimming the jib tight. I am much bigger and stronger, and this was not a problem for me.
2nd I used the Murry's # 01-3120 System. I love it! Everything works great.
The second option is much better.
David