26x4.0 fat bike inner tube. These are typically made from durable butyl rubber and are designed for use with fat tire bicycles, which are suitable for riding on sand, snow, and rough terrain. 
Key information:
Size: 26 x 4.0 inches (compatible with wide tires). 
Material: Made from high-quality butyl rubber for better air retention, shock absorption, and puncture resistance. 
Valve Type: Schrader valve.
Application: Ideal for fat bikes, mountain bikes in tough conditions, and e-bikes with oversized wheels.