I have bought two sets of these, so far.
I am relating my experiences with them, in case it helps someone considering these.
They are the oriiginal style Mato 3:1's as shown on the like;
Gearboxes
http://matomart.com/prodview.php?p=567
Connectors with wires, these will be needed, unless the one’s on the stock gearboxes are removed and used;
http://matomart.com/prodview.php?p=491
My use of these is limited to HL Tiger I's. I use stock suspension and original plastic tracks.
1.) First set was bought at the Toronto Hobby Show, along with aHL Tiger I, in Nov. 2010.
These were very good, no issues, they move the Tiger at a maximum scale 16 MPH
They make the Tiger I very nice to drive, very controlable.
2.) Second set was ordered a couple weeks ago, along wiith another Tiger I for my SLU project.
One Gearbox was very good, the sprocket shaft on the other was about 10 degrees off level, this resulted in gears that were bound up and even if it had run, installation would have been impossible.
Contacted Mato, got a return number, sent it back. In just over a week (mostly Canada Post time), I got a replacement, it is very good.