That "bivvy" is a borderline tent, both in cost and weight. A "true" bivvy would be about one-quarter of the weight, and easily one third of the cost. What is nice is that there is a continuum ruanging from 8 ounce bivvy sacks on up to one person tents weighing about 24 to 32 oz (and higher). You can pick whatever suits your fancy and circumstances.
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Geezer in Chief