I bought this bag after buying the Topeak medium-sized wedge bag with straps and being disappointed with that bag in terms of its size (too small, not in cubic inches, but in having such a narrow nose), attachment mechanism (too slow) and accessibility (hard to reach and move the zipper under the saddle). This bag addresses all of those problems and then some.Some details. This is a large bag, but not really too large. You need a lot of exposed seat post, however, to be able to attach both straps (a minimum of 7" by my measure, from below the saddle rails). The bag holds a lot -my wallet, sunglasses, spare tube, wrenches, energy bars, small pump etc., quite comfortably. The mesh net in back, in addition to holding a water bottle or other drink, could, instead, hold a windbreaker vest or thin jacket (if you don''t mind crumpling). Very useful.
Access to the main, deep, compartment is from the left side zipper (looking forward from the back of your bike). The flap of the compartment has a nice mesh net inside. There is a right side zipper and compartment that is very thin (not deep) that could be used for tire irons, a very small pump, maps, etc. (elastic loops are on the inside wall). The interior chamber goes all the way up to the top of the bag, which is good to squeeze in a larger pump, but might otherwise be difficult to use efficiently without piling items on top of each other.
Attachment to the bike, with Topeak''s "fixer" mount -is very convenient. One catch is that the included Fixer 25 mount is a fixed width (in terms of distance between saddle rails), which means it has to go on the bottom of your racing/touring saddle''s rails. If you rely on having your saddle in its most front-forward position, you''ll have to slide the saddle back about 3/8" to get the quick mount piece in place. As for the velcro seat post ties, they are much improved from Topeak''s wedge bags. The MondoPack attaches the straps to the bag by a loop, and not by being sewn or fixed in place. This means that you can adjust them so that you don''t have a lot of excess strap left over if your seat post is thin (a real problem with Topeak''s wedge bags).
I jammed the bag full for a Century ride the other day and did, on occasion, feel my legs mildly hit/rub it, as the width of the bag can exceed the width of a narrow racing/touring saddle. But I think this wouldn''t be an issue with a normal load (or with saddle positions that aren''t as far back as mine) and, in any event, I stopped noticing it after a few miles. But it conceivably might be an annoyance for others.
4-1/2 stars in my book. Half a star deducted for the limited adjustability of the Fixer 25 mount and the possibly excessive width of the bag. But highly recommended in all for those needing a large bag -I''ll definitely be keeping and using it.
EDIT 5/12/12 -If you have the some problem I did with the Fixer 25 eating up needed saddle rail real estate, you might try the Fixer 11. It''s wider and angled so it will fit on the portion of the saddle rails going up to the saddle (instead of the portion on which your seat post slides and clamps). I''ve made it work on a bunch of different racing-type saddles (Romin Evo Pro, SMP Pro, Terry Fly Ti).
Buy Topeak Mondo Pack Hydro with Fixer 25 with Water Bottle Pocket Now
I bought this specifically to use on the MS Delaware 2012 Bike to the Bay (I know there are plenty of rest stops and SAG vehicles but I prefer to be as well prepared as possible!). I wanted a bigger pack to carry a few more items than usual, including a thin rain jacket. I was able to pack everything I needed with room to spare and the jacket fitted snugly in the rear pocket (which is actually designed to fit an extra water bottle). My usual pack is also a Topeak, so this one just attached using the existing Topeak F25 Wedge Pack Fixer attached to my saddle. Very happy with this purchase.Read Best Reviews of Topeak Mondo Pack Hydro with Fixer 25 with Water Bottle Pocket Here
I returned this item for 2 reasons:1. The water-bottle/stuff pouch on the outside of the bag makes contact with my rear wheel. I measured from the seat post clamp to the top of the seat post and there was 6.25" of exposed post. I ride a medium-sized frame 54.8". I would guess you would need at least another inch of clearance, whether it be from frame or seat, to make this bag work for you.
2. The bag rubs the back of my thighs while pedaling. I have big thighs, so I have a problem with rubbing on the Velcro strap which attaches this bag and other Topeak under-seat bags (I also own the Aero Wedge Pack, w/ Fixer F25, Medium), but in addition to this annoyance my legs also made contact with the outer edges of this bag itself, which I found more noticeable while riding.
Overall I still rate this bag 4 stars because it seems to be made with the same high level of quality and functionality as many of the other Topeak products I own. However, those of you with short, thick legs like mine be warned this may not be the bag for you.
I ended up going with the Topeak DynaPack Bicycle Seat Post Mount Bag with Fixer ,which provides a lot more seat post clearance and twice the space.
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