Which Pelton & Crane light spring assembly to order?

Which Pelton & Crane light spring assembly to order?

Wondering what the difference is between the two Pelton & Crane light spring assemblies that DCI offers? The only difference is the spring tension. PN 2734 is for the track/ceiling light and has a heavier spring. It's marked with a red stripe running down the length of the spring for easy identification.  PN 2733 should be ordered for unit mount lights.