This bag was bought to replace a frame bag.
The bag is easy to install.
Right now it holds two tubes, a mini morph pump and some other tools. It still has adequate space to hold a great deal more for a day trip.
My Lezyne light clips on to the back and is highly visible.
The bag is waterproof, made extremely well and acts as a half fender for the rain.
It is a purchase you will not regret.
Better than all the rest, regardless of price but cheaper too! This is a review of the largest version which is slightly over 4L. Very light, easily to load, watertight. Most critically, it is very adjustable to the load, always positioning the light mount perpendicular. I mount my radar unit there, and it secure and easy to position. This thing is great for carrying extra clothing in winter.
Very happy with the quality of the seat bag. I purchased the 4.1L bag which is large enough to carry a pump, tube, repair kit, water bottle, and additional snacks. Would be nice to have a pressure release valve but I have been able to vent the air manually with no issues.
Seat bag attaches securely to the rails on your seat. Best to remove seat and post from frame for easiest attachment. Bag is the right size for carrying emergency tools, spare tube, possibly a thin jacket. I attached a Lezyne Alert Drive light to the rear of the bag for best visibility.
I've purchased several of these seat bags. They tuck under the seat. They adjust for the distance between the seat post and the attachment point. They are well designed, lightweight and waterproof. Reasonably priced.