The Source Spinner Pro is designed to be two packs in one. The main compartment, which contains the hydration bladder, is supplemented by a front organiser section, which can be removed when you don't need it. This is very useful, because it means you can use the Spinner Pro both as a lightweight racing pack and for bigger adventures.
The organiser section weighs 90g and sits on the outside of the pack, secured by two adjustable plastic buckles. It also doubles as a helmet holder. The inner pocket layout is generous, with multiple mesh stash pockets.
The mesh outer pocket is not zippered but is easily accessible and is perfect for stashing an inner tube or race food. The elastic cord on the outside will hold a jacket or other clothing in a pinch too.
We loaded this floating front section with a tube, multi-tool, energy bars, phone, keys and wallet and there was still some space to spare. With all this additional weight in it, the front section did make itself known and created some additional noise – in an ideal world, a pack should be barely noticeable when you're riding with it.
As a whole, the pack is small and light (420g including the outer section), which certainly helps make it comfortable and stable. On hot days, the basic ventilation system won't stop you from getting sweaty where the pack sits on your back, although the mesh straps do help remove some heat.
The main pack is slim and doesn't offer much storage beyond the insulated bladder compartment and the low, narrow zippered section that sits in front. There are some mesh side pockets, but they aren’t easy to reach while on the bike and are too small for anything more than a gel or two. There's also a simple pump loop, which lines up with one of the mesh pockets.
Filling the side-accessed bladder is easy, but it isn't the quickest, and there are better race packs if an urgent refill is needed.
Source supply its hydration bladders to many other pack manufacturers, and as expected, the taste-free 2-litre Widepac bladder is superb. Featuring a slide-lock closure, the bladder opens wide for easy filling and cleaning. Even with a bit of force, we experienced no sign of leaking from any part of the bladder.
The twist-lock bite-valve is a huge improvement on previous Source versions and the water flow from it is generous. The tube holder on the pack doubles as a bite-valve protector and we quickly got accustomed to using this while riding. The tube holder does create a loop in the hose, and that took some getting used to – it got in the way a little when we dropped our elbows while climbing.
The insulated hose is an easily overlooked addition, but we appreciated it on smoking hot days as well as in bitterly cold conditions.
Overall the Spinner Pro is a solid option, with a competitive weight and quality bladder. The downside was that although we love the idea of the modular design, we were a bit too aware of this part of the pack while we were riding.