The outer shell of the Torpedo is made of the highly waterproof and breathable eVent fabric. The shell is made up of only two pieces of fabric sewn together, with the seam taped to ensure that the shell is completely waterproof - this process of minimal stitching ensures you get the most waterproof bag possible at minimal weight. However, this lightweight design does not compromise on durability. The weight and thread size used is twice that typically found in a standard down sleeping bag, providing a greater degree of protection from rips and tears but retaining an lighter overall weight.
The two-layer outer is comprised of the outer face fabric and the most breathable eVent membrane available. The face fabric has a very smooth "spuntouch" finish that enhances durability and is very good at holding a strong DWR (Durable Water Repellent) coating. Another huge benefit of this material is that it is remarkably soft which means, unlike most other waterproofing fabrics, it does not rustle - thus ensuring a quieter night's sleep
The final line of defence from water comes in the form of the Riri Aquazips. These zips have plastic moulded teeth that mesh together and actually form a highly water resistant seal. Although the seal has only a modest hydrostatic head, it is a huge improvement when compared to the standard zip coils featured on most clothing, packs and sleeping bags. Like the rest of the sleeping bag, these zips are built to last; the slider has no contact with the PU coating so any wear and tear through abrasion is eliminated.
Crux have used 850+ fill power Polish Goose Down, providing the highest level of warmth available at the lowest weight. The loftier the down means more air trapped and, as such, the more effective and warmer the insulation is - 850+ Goose down is amongst the highest quality insulation available if not topping the list. Using only Polish goose down also guarantees the integrity of the means of its collection, and the quality of the fill power.
The technically minded will appreciate the design ingenuity that has gone into the construction of the Torpedo sleeping bag. While it looks simple, the inner of the bag is comprised of a system of vertical and horizontal baffles whose placement has been carefully calculated to maximise the thermal efficiency. Designed to hold the down in place around the body of the sleeper, these compartments maximise the performance of the bag as a whole. The torso area of the bag uses the vertical V-tube baffles to keep the body's core as warm as possible by holding the down in place more effectively. This is compared to the lower half and back of the bag, which use an overlapping system which prevents any cold spots called slant box-wall baffles.
The main culprits for heat loss in a sleeping bag are usually the cold spots created by the zip and the hood opening. Knowing this, Crux have put in double baffles to cover the zip and a full neck baffle with shock cord adjustment to stop any draft creeping in during the night. This is as well as the adjustment cord around the hood; it all combines to give you a snug fit and a warm night's sleep.