The image below can help guide you to the correct part number you need if you are not familiar with the terms used to reference the undercarriage parts. Many people refer to them as wheels and pulley but in the industry there are several uncommon terms for the rollers, and idlers. Place your mouse over the image below and the drive sprocket, rubber track, front roller (under the sprocket actually in the rear of the machine), bottom track rollers and front idler will pop up with the correct term and link for you to learn more. Don't hesitate to call with any questions you have. Each manufacturer has different terms for these parts. A rear idler on a New Holland is referred to differently on a comparable Takeuchi track loader.
The image below is from a Takeuchi TL 150 undercarriage, the TL 250 is exactly the same. The Takeuchi TL 140 and TL 240 are very similar, just with one less bottom roller on each side. The TL 130 and TL 26 type series are signifcantly different as far as part numbers so please see their categories for more detials