With days getting longer, its officially big bag season!  That’s right folks, time to pack a lunch, extra clothing, tools, and a handful of spares for some backcountry adventure.  At a claimed 20L cargo capacity (M/L size), Osprey’s Manta 20 pack just meets my usual all-day ride carrying requirements.  Given my experience with its cycling-specific nephew the Raptor 18, I knew to expect a well-built bag with an excellent reservoir.  Read on to see how the multi-sport Manta is a better bag for bigger days…

Like the Raptor 18, the Manta 20 is an impressively built bag.  Even on the shop floor, all of the materials seem well-chosen and the hardware is of consistently high quality.  As it has to be- the Manta is backed by Osprey’s “All Mighty Guarantee,” under which the company “will repair for any reason, free of charge, any damage or defect in our product – whether it was purchased in 1974 or yesterday.” Dang.  My experience with the Raptor and since the Manta 20’s arrival last fall suggests that this particular bag won’t be going back to the factory any time soon-  dirt and salt stains aside, it’s looking virtually new.

A narrow pack for its 20L capacity (in the M/L size- the S/M size will hold 17L), the Manta is organized in three basic layers. At the rider’s back is a simple suspension system consisting of a pair of LightWire bows that suspend a mesh layer above a ridged foam back panel.  Though this may sound on paper like the suspension systems used by Deuter and VauDe, Osprey’s is much lower profile and allows the mesh to rest directly on the corrugated foam.  Is it any cooler than the foam alone?  If so, I haven’t noticed, but the frame’s structure does seem to help the pack manage heavy-ish loads well.

Working out from the suspension system is a bladder pocket bracketed by the ridged AirScape back panel on one side and well padded on the other. Osprey’s idea is that the bag’s structure will actually serve to squeeze the bladder to increase water flow and minimize sloshing. In practice, the bladder didn’t flow noticeably better than CamelBak’s recent models, but it is the freest-flowing non-CamelBak bladder I’ve used.  The dedicated compartment really does make inserting the bladder into a loaded pack easy. Further easing bladder insertion and minimizing sloshing is a semi-rigid panel in the bladder itself and a rigid plastic handle, making the HydraForm easily the most engineered bladder I’ve come across. Though the threaded cap can be a hassle to get started, the handle makes filling the bladder easy and a silvery anti-microbial material helps to keep funk under control.

Where it seemed as though the Raptor 18 was overly compartmentalized, the Manta 20 allocates over half of its capacity to a large single pocket.  For big days or light commuting, this is a big advantage- easily accommodating bulky layers, changes of clothing, and pizza-filled Tupperware.  Granted, small items can sink to the bottom, but I haven’t had anything (within reason) not fit and the long zipper provides good access.  A decent-sized valuables pocket is suspended in the main compartment and lined with soft fabric to protect expensive electronics.  Four compression straps do a good job of keeping differently sized loads under control and everything compact.

At the outside of the Manta is a 2/3-height pocket with a couple of mesh organizers and a key tether and on top of that an open-topped pocket made of a stretchy material.  The first seems to be a good place for smaller items and the second, because it’s hard to reach while riding, became more of a trail trash receptacle than anything else.

The waistbelt’s two zippered pockets are generously sized, with each able to take in a couple of Clif bars and a gel.  There is no padding between the pockets and rider, though, so leaving a mini-tool to bounce around in one can lead to funny little bruises- throw it in with a skullcap and it’ll be fine.  Shared with the Raptor, the Manta’s shoulder straps are some of the most comfortable I’ve worn while remaining reasonably breathable. The zigzag-cut foam seems to provide a bit of suspension, most noticeable when pulling the loaded pack on.  They’re fine for 3-4 hour rides with moderate loads, but can be overwhelmed when the bag is stuffed full, making it important to wear the pack low enough to let the waistbelt share some of the load.  Also shared with the Raptor 18 is the “straight ErgoPull™ hipbelt closure,” which seems needlessly complicated and is difficult to adjust while riding.  As a skinny guy, I have the adjusters bottomed out- anyone with a sub-30in waist will likely be out of luck.

During a freak spring snowstorm, I was happy to take advantage of the bright red rain cover that lives at the bottom of the bag- nobody likes stuffing their valuables into Ziploc bags as the skies open up.  The Manta 20 replaces the Raptor series’ helmet bungee with a single daisy chain- not quite as secure, but something that actually works better for several of my helmets.

The HydraForm bladder’s bite valve delivers plenty of water and its angle can be adjusted easily- it does seem odd that the ‘lock’ position is straight out though- rotating it to sit in line with the drinking tube would expose it to less crud during handling.  After about 6 months’ use, my first bladder had started to drip as the clear rubber cracked- an annoyance, but to their credit Osprey seem to be very free with spares and the second has been perfect.  I’ve been using the Nalgene-made bladder in other packs and it has worked well- all of that structure sure is nice when the alternative is trying to force a shapeless monster into a loaded pack.

The bite valve has a strong magnet in its pivot, which mates to another in the floating end of the sternum strap. Because the sternum strap’s free end is so heavy, it tends to flop around a lot when not connected. It would be nice to move the magnet to one of the shoulder straps, which would also allow its use on warm days when the sternum strap isn’t wanted.  I often find myself tucking the sternum strap behind the shoulder strap to keep it from swinging around and hitting by bell on steep climbs (a magnet-delete kit is available aftermarket from Osprey, and I probably could punch the little guy out if I really wanted to).

As with the Raptor, the Manta 20 is very clearly biased toward right-side hose routing. The bladder’s hose is more than long enough to be run from the right side of the pack (where it exit’s its zippered pocket) under the load lifter straps and down the left strap.  It’s not a big deal, but the left shoulder strap’s hose routing isn’t quite as nice or flexible as the right’s- why make them different? Plenty of riders prefer to take their left hands of the bar to drink (covering the rear brake and controlling the bike with their dominant hand) and it seems odd not to accommodate them.

When all is said and done, though, these minor complaints are far from severe enough to keep me from recommending Manta.  It’s narrow footprint and effective compression means that it doesn’t ever feel too big for a 2-3 hour ride, and its capacity makes it capable of somewhat longer rides.  The Manta’s claimed 20L seems like a stretch- it is noticeably smaller than other companies’ 20L bags, making the bag’s capacity marginal for really big days- if those or commuting are in the cards, 25L and 30L Mantas are also available.  Well thought out and easily one of the best made packs I’ve ridden, the Manta 20 (with bladder) is also a good value at $130.  For an extra $10, though, the Manta 25’s extra capacity and mesh side pockets would get my vote.




  1. Binny,

    I’d give the Manta 20 a 4/5, with a thumb taken off for the handful of small opportunities for improvement outlined above. For what it’s worth, I’ve never seen a 5/5 pack!


  2. surely you mean 2.0 liters, and not 20 liters. A 20 liter bladder would hold 5.28344102 gallons. . .and at, say 8lbs per gallon, that’s a lot of volume and more than 42 pounds.

  3. The “liters” being referred to is a measurement of the cargo capacity of the pack, not water capacity. Impressive math skills though. Maybe you should stick to doing math.

  4. I’m absolutely positive, have no doubt, and cannot even think of a way that someone could not make a “20 Liter” Bladder whose volume was accurate down to 1/100,000,000ths of a gallon. It’s always important to use all the numbers shown on the calculator.

What do you think?