the very lightweight tr4 is a true backpack miracle. all essential features packed into 4l volume, with h2o compatibility and air mesh back. the very lightweight tr4 is a true backpack miracle. in the main compartment you will find a mount for 2l hydration bladder and a zippered pocket. jacket or protectors can be stored in the stow pocket and small items in the additional front pocket. helmet attachment and a reflective attachment for a rear light round out the package.