MSR Twin Sisters Review
Cons: Heavy, lots of condensation when used in three-season conditions.
Our Analysis and Test Results
The Twin Sisters is the largest and most spacious two-person pyramid shelter we've tested. It provides two people tons of space to spread out and to store gear. The increased width compared to other two-person mids tested is particularly useful in strong winds that blow in the sidewalls. With smaller shelters, this reduces the amount of usable space to a tiny area that's not particularly comfortable. But the larger space in the Twin Sisters lets you be comfortable even in high winds. We spent a few nights in the Twin Sisters on 25" sleeping pads and were able to keep our sleeping bags dry in the rain; this isn't possible with many other mids. The shelter is long enough for six-foot tall people to sleep comfortably and store backpacks at one end. Two doors make it easier to enter, and exit, and each door flap can be rolled aside to create a large entrance. Luxurious!
The Twin Sisters uses a reasonably strong 30 denier ripstop nylon that's coated with silicone on the outside and polyurethane on the inside. The seams come taped from the factory, which is convenient. A full silnylon fabric would likely be stronger and more durable, and would increase the cost.
The Twin Sisters' design has steep walls, a moderate catenary curve that makes it easy to apply a lot of tension to the walls. We found this mid to be easier to pitch properly than the GoLite Shangri-La and similarly easy as the Black Diamond Beta Light. The two-pole design catches more wind than the single pole Mountain Laurel Designs DuoMid, and two poles are slightly more of a pain to maneuver around inside the shelter, but the Twin Sisters performs very well at what it's designed for--winter mountaineering. This model is the only shelter we've tested that has a snow skirt that successfully blocks spindrift (and is very hard to dig out of the snow in the morning). It's steep walls shed snow better than unipolar mids.
The Twin Sisters has adjustable ground level tieouts! This detail is an excellent feature that's missing on the Black Diamond Beta Light, GoLite Shangri-La 2, and Rab Element 2. We found that these significantly increase ease of pitching and make it easier to adjust the fly tension without getting out of the tent (reach a hand out from underneath if the snow skirt isn't buried).
Weight and Packed Size
The Twin Sisters tarp weighs 31.9 oz. on our scale. The poles weigh an additional 11.5 oz., and the stakes weigh 3.5 oz. Stuff sacks for the poles, stakes, and shelter add around 3 oz. (we didn't weigh them).
Even without the poles, the Twin Sisters is the heaviest mid we've tested and the heaviest product in our Ultralight Tent Review. Other types of shelters, such as the Hyperlite Mountain Gear Square Flat Tarp also work well in winter but require more technique to pitch and don't perform as well in heavy snow loading (you need to be more attentive to how much is accumulating).
Being a mid, the Twin Sisters doesn't offer much adaptability. It must be pitched in the same way every time, so campsite choice becomes key. Not that this is very challenging in most environments. Thru-hikers might prefer an A-frame or flat tarp for its greater adaptability to sub-optimal campsites.
The snow skirt limits ventilation in three-season applications and requires you to open a door for any significant amount of ventilation if the snow skirts are under snow. The Twin Sisters is very prone to condensation, which is typical for winter mids. It's rather heavy for use anytime other than the winter.
Expedition mountaineering, backcountry skiing.
The Twin Sisters is a great value if you if want something for winter only.
— Chris McNamara and Max Neale