One 10" Rubber Middle Bogie Wheel to fit CAT 247B2 247B3 257B2 257B3 257D (reference number 2781261). The bogie wheel runs inside the track and helps support and guide it on the undercarriage, and this is a direct replacement for the original wheel on these models. Sold individually.
I got this for my 2011 257b, it was a perfect fit and seems to be good quality. Only time will tell with durability. I recommend this product if you don’t need bearings. I will probably switch to aluminum middle bogies once I need bearings.