ROCKBROS Bike Saddle Bag Bike Seat Bag with Water Bottle Holder Bicycle Bag Under Seat Waterproof for Road Bike

First, I did not rate durability and sturdiness, as I just received the item. This design is really well thought out, including the bag, which has ample space for an inner tube, a CO2 cartridge and valve, tire levers, multitool, etc. The water bottle holder is also well designed, not only with a snug fit, but a nice elastic cord which can fits around the bottle for security while riding........BUT, AND THIS IS A BIG BUT, the mounting mechanism is poorly executed. There is a screw-on mounting bracket which clamps to the rails on the underside of the seat. To that, the bag has an integrated plastic rail which slides into, and 'locks' onto the bracket (there is a flexible latch/tab you can push to disengage the locking mechanism to remove the bag). Inserting the water bottle into it's holder reinforces the 'stop' limit on the rail and all is well, BUT when you pull up on the water bottle to remove it, the latch/tab disengages with very little force and suddenly the bag is no longer firmly attached. The only hack I've been able to create is remembering not to pull straight up, but twist and pull up somewhat gently to avoid disengaging the latch. This is manageable but not ideal or acceptable. Rockbros should redesign/strengthen the latch mechanism.

The durability and sturdy may vary depending upon the user not the manufacturer.

Convenient and cool.

it looks good but doesn't have the right angle for the rear light