Carburetor Kit.  For Walbro HDB carburetors.   There were 3 different brands of carburetors installed on the 600 series saws, make sure you have the Walbro brand carburetor before you buy this.

This fits the following saws with the Walbro HDB carburetor:

McCulloch Pro Mac 605

McCulloch Pro Mac 610

McCulloch Pro Mac 650

McCulloch Pro Mac 655

McCulloch Eager Beaver 3.7

McCulloch Timber Bear

McCulloch 3.4

McCulloch Pro Mac 5700