Friulmodel Sprocket & Idler Sets

In some instances they are more accurate than the kit items.  Also, if the vehicle has "dead" tracks, and the kit has one piece tracks, it will allow for a more realistic sagging of the links (if not overdone). if you"need" them is up to you.

Sometimes the kit-supplied sprockets and idlers aren't the right size or have the right tooth pitch (usually a dimensional accuracy issue as Bronto mentions) and the Fruil links won't fit as as result, requiring a replacement to make them work. Sometimes Fruil includes them in their link set to avoid problems, sometimes not, all depends on the kit and the set. HTH!

Thanks guys!!

Is there a way to decide if I need a  Friulmodel Sprocket & Idler set for the tracks when I order the tracks? Or do I have to build the tracks and try the model set first before I know I will need them?

If your kit was manufactured before 1995, you will probably need the sprocket and idler.  After that, only if it's not from one of the "Big Three".  The only set I ever used was back in the early-mid 90s for the Tamiya Pz IVD because that kit has 40cm sprocket/idlers rather than 38cm.  I used the Fruil s/i with Kasten tracks which was very high-tech back in 1994 or so.  

Since most of those Fruil sprockets and idlers were made a decade or more ago, the injection-molded ones are probably as good or much better today.