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Will it work with a dropper post?
No. This pack attaches to the seatpost, so it needs exposed post to hold on to. Drop the post and the pack is in the way — that is the conflict, and no strap arrangement gets around it.
From how Ortlieb describe the attachment. See the source.
How much room does it need?
This pack measures 48cm long and 22cm deep. Length is how far it reaches behind your saddle, and it's what drives sway — a long pack is a longer lever on the seatpost. Depth is what competes with your rear tire once the pack sags under load.
Across the 18 seat packs we hold dimensions for — which run from 24cm to 67cm — this one reaches further back than 8 of them, and hangs deeper than 10.
The other number that decides this — how much seatpost you have showing above the collar — depends on your leg length rather than your frame, and makers almost never publish a minimum. So measure from the top of your seat collar to the bottom of your saddle rails, then check it against the mounting hardware on the product page. If you run a dropper post, look for a pack that mounts to the saddle rails alone.
Check against your measurementsOrtlieb Seat-Pack QR 13L — Specs & Analysis
Manufacturer specifications, compared against every other seat bags in our database. We do not test gear in the field — we measure, verify, and compare.
Ortlieb's Seat-Pack QR pairs their signature waterproof construction with Seat-Lock hardware that takes the whole bag off the bike in seconds. The QR is sold in 7.5L and 13L; this is the 13L. Note that the quick-release hardware is why it weighs more than the strap-mounted Seat-Pack of similar volume — you are paying grams for the convenience of lifting it off at a cafe stop.
Who Is the Ortlieb Seat-Pack QR 13L Best For?
Riders who need maximum waterproof seat storage with quick-release convenience. If that describes your riding style, the Seat-Pack QR 13L should be at the top of your shortlist. It sits in the Seat Bags category alongside 17 other products we track.
How It Compares
At 625g and $215, the Seat-Pack QR 13L is 483g heavier than the lightest option in this category (the Revelate Designs ECOPAK Shrew Seat Bag at 142g). The most budget-friendly option is the Topeak BackLoader 10L at $70.
The price-to-weight ratio comes in at $34 per 100g — a premium price point, but you're paying for quality, materials, and design that justify the investment for serious bikepackers.
What We Like
- +Seat-Lock hardware takes the whole bag off in one movement
- +IP64 welded waterproof construction
- +13L holds bulky sleep-system components on most setups
- +Hard mount rather than straps, so nothing to re-tension
Watch Out For
- −625g — the quick-release hardware is heavy for the volume
- −The mount is proprietary; you are in Ortlieb's system
- −48cm is long enough that rear-tire clearance needs checking
The Bottom Line
We haven't scored the Ortlieb Seat-Pack QR 13L, and neither has anyone else we can cite. It's here for its verified specifications and dimensions, which is what the fit tools run on — a score is an editorial judgement, and we don't hand one out until someone has a basis for it. What this page can tell you is measured: 625g, $215, and how both sit against every other seat bags product we track.
The price and weight above have not yet been checked against the manufacturer's own page. We are working through the catalogue and saying so as we go, rather than letting silence imply otherwise.
Specifications and dimensions come from the sources listed above. Where a page draws on first-hand riding, it says so.
How the Seat-Pack QR 13L compares
Against the bags people cross-shop it with, measured rather than reviewed — including how many real frames each one fits.
How it compares
Against the 18 seat bags we hold published specs for.
At 625g the Seat-Pack QR 13L is lighter than 2 of 17 alternatives we track, which makes it among the heaviest we track. The category median is 466g.
At $215 it undercuts 4 of 17 of them, against a median of $170. That works out at $34 per 100g — below the $36 median for seat bags.
Weight and price come from published specifications. Cost per 100g is a blunt measure — it rewards light gear and says nothing about durability or whether the thing works — so treat it as one input, not a verdict.
More in Seat Bags
Seat bags extend behind the saddle, carrying gear without the need for a rear rack.