Utilize that empty space on your bicycle's frame triangle with a frame bag!

Bicycle frame bags are a convenient and out-of-the-way place to store extra gear on your bike. Bike frame bags can be used in a wide variety of circumstances from local commuting to long distance touring to bike packing and just about everything in between.
The narrow profile of bike frame bags ensures that they are kept out of the way of a rider's movement on the bike. Their attachment straps are designed not to interfere with the bicycle's cables and housing. Bike frame bags also have a very minimal impact on a bicycle's handling, especially when a rider is out of the saddle or cornering. Unlike bike pannier bag and bike rack setups, which do tend to change bike handling to some degree, bike frame bags usually go unnoticed by a rider, much like saddle bag for bike.