Dinky Toys 22f 80c 801 817 Early Army Tank Red Tracks Treads Pair.
2 per model. Priced per pair for a correct match on your model.
Also available in black which are the same size and will fit any of these models.
Track dimensions are measured at full stretch internal 88mm which implies and overall length of approx 176mm. Width is approx 6mm, while they are approx 2mm thick.