This tire from Kenda is great for mountain biking. They are 26" and 2.1" wide. The ETRTO is 54-559. They have 22 threads per inch.
• 22 TPI (threads per inch)
• Tire size is 26" and 2.1" wide
• Tire tread K-816 and ETRTO of 54-559
• Great for mountain biking