If you want to carry just a couple of items when you ride your bike, this bag does the job without hampering the riding process in any way.
The Topeak Aero Wedge bag fastens beneath the seat of your bike. Because it has a rigid bracket it does not swing at all when you ride. There is a plastic clamp-type bracket that you need to screw around your seat frame wires. Then you just slide a plastic tab that is permanently fixed to the bag into the bracket you just mounted. There is a velcro strap that then encircles the seat post tube to keep the front end of the bag stable.
Just to the back of the midline of the bag is another zipper which allows the bag to expand slightly. This is a good feature if you have a few small tools or hard items that you want to secure in the bag so that they won’t rattle around. You can zip it closed and the bag will be a little bit smaller, or open it and the bag will be a little bit larger..
The primary opening of the bag is a zipper that opens three sides of the square on the back of the bag. Located on this flap is a small mesh pocket which is nice if you want to perhaps keep your cell phone from banging on a couple of tools in the main compartment.
This particular bag is the Medium size. It is about 3.5 inches square by 7.5 inches long, tapering at the front end. The specs say that it has 60 /80 cubic inches (closed or expanded). It is made of 1000 Denier Cordura nylon. There is also a small webbing loop on the “door” flap where you can mount a tail light. And it has a reflective stripe on the back.
My husband has this mounted on his bike. He generally carries just a jacket and his cell phone in it. The jacket stuffs easily into the expanded bag. He says that what he likes best about the bag is that the rigid attachment means that the bag does not swing at all from side to side while he is riding. He finds bags that do this very annoying. He also really likes the little mesh pocket on the flap.
The only possible warning is that you need to check your seat frame to be sure that the wires are angled near the back of the seat. If they do not have this angled section the bag will not mount properly.
"Age Level?" I have no idea how to rate that. It's not a toy, it's a bike bag.
Aero Wedge bag on Amazon