Ortlieb Seatpost-Bag Medium

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Versatile and lightweight: one simple tool-free maneuver is all it takes to attach or remove the waterproof Seatpost-Bag. Integrated mounting and roll closure allows tight packing.


Best. Seatpost. Bag. EVER.

The Ortlieb Seatpost mounted bag is great for people who don’t want or can’t install saddle mounted bags because you can switch the bag between bikes frequently.

The Ortlieb Seatpost Bag medium has the integrated ratchet mount that allows you to quickly install and remove the bag from your bike and A fixing for a rear light or reflector.

Please note that this product is not recommended for carbon fiber seatposts.

The waterproof PU coated nylon and Cordura fabric paired with the roll closure will ensure that your gear stays dry. The Small Ortlieb Seatpost bag can hold just about 1.5L

These bags stick out just enough to help minimize the dreaded rooster tail from dirt and water.

  • Individually adjustable ratchet closure compatible with seat post diameters from 25.4 mm to 34.9 mm (not suitable for carbon fiber posts)
  • 3M Scotchlite reflector
  • Fixing for rear light
  • Maximum carry weight: 2.5 kg / 5 Lb
  • Dimensions: 5.5 x 13.8 x 5.9 in / 14 x 35 x 15 cm
  • Weight: 15.0 oz
  • Volume: 244.1 cubic inches / 4 Liters
    • All


    products are backed by a 5-year warranty against defects in material and manufacturing.
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Dorothy P.

Ortlieb Seatpost-Bag Medium

This is a great bag. Not a drop of water got in on a six day tour with a fair bit of rain. At first I thought it was going to be too small for my needs, but I fit my tools, a large sunscreen, several sundry items and my rain jacket with some room too spare. Best of all, the rain jacket fits nicely on top of the bag tucked under the straps which gave me even more room. Folded shut and snapped to the sides with no problem.

I did have a lot of trouble strapping the bag onto the seat post. The directions (an Orlieb shortcoming) are not clear to spatially challenged people such as me. Just pictures, no words. Customer service tried to help but I was doing it right, just needed someone with more muscle to snap it into place. A passing guy took care of it in two seconds, but I needed help again the next time. I think the third time I finally did it alone. Really wasn't a big deal; only reason to take it off is when transporting bicycle on the car. And the clasp is so secure that that is really just a precaution. Might not bother for a short ride...on the other hand, it ain't cheap so sure don't want to lose it!