I have several 120 cc snowmobiles that we use for racing and playing. These are small childrens machines powered with "lawn mower" type engines. All of the major manufacturers sell these machines and they are all put together with very similar components. I have a few older posts about them here, here and here.
These machines use a 12" wide track that is normally driven with involute drivers that engage the track on the rubber "lugs" on the inside of the track. After a lot of hard use the track and drivers on our Skidoo Mini Z wore out. In this photo you can see the lugs sticking up on the right side of the track, just outboard of the clips. The left side of the track is supposed to have lugs also, but they have all been ripped off. This track is interesting because there is no windows in the track. The clips are attached to the track with no open holes.
This photo shows a Polaris track with nice tall lugs next to the clips. You can also see that there is a "window" between each clip.
The track in the Skidoo was obviously junk and the drivers on the drive shaft were pretty worn out. In the above photo you can see the old drive shaft on the right side (I cut it in half to make it easier to get out of the old bearings.) As you can see the teeth on the black plastic drivers are rounded off.
The drive shaft on the left side is a Polaris shaft with new "anti ratchet" type drivers. These drivers are designed to drive the track be engaging the windows on the track and pushing on the clips. This set has 5 teeth rather than the original 4, this will change our gear ratio quite a bit, making the machine faster on the top end but given up some low end torque.
I ran out of photos, but the new Polaris track and drive shaft fit right into the Skidoo with no problems.