The Outdoor Research Helium bivy is a lightweight hooped bivy shelter made of Lightweight, waterproof and breathable Pertex Shield+ fabric.
This is the most spacious bivy on test, easily swallowing a 6ft 2" tester, Exped Downmat and Rab 3 season sleeping bag with plenty of room to spare.
The hoop ideally needs to be pegged out to be fully effective but once it is the functionality of the bug net comes into play, something we really appreciated when we started getting eaten alive on Pen Y Fan.
The floor fabric is a robust 70D ripstop nylon which is reassuring when pitching up on rough ground. The 30D Pertex Shield+ upper material is fully waterproof, and is further reinforced by taped seams. The fabric is touted as being highly breathable but we experienced a fair amount of condensation in the Helium with the bug net zipped up, possibly down to the users breath inside the bag as well as being a hot (sweaty!) sleeper, we'll reserve judgement until further testing.
The sleeping pad straps are a handy addition but probably add a few grams to the overall weight of 510g which puts it about mid-range in terms of the other bivys on test.
At around 35cm x 15cm the Helium has the largest packed size on test but it's still tiny compared to most 1p tents.
Overall, the Helium is a lightweight, feature rich bivy bag which, at £135 represents good value for money, especially when compared to other hooped bivy bags on the market, just watch out for condensation.