The Pipedream 400 has been the benchmark sleeping bag for UK ultralight backpacking for years. Alpkit has iterated on it steadily without losing the plot, and the current version earns its reputation through numbers that are hard to argue with: 400 grams of 850 fill-power hydrophobic down, comfort rating of -1C, lower limit of -6C, and a packed weight of 865 grams.
That combination covers genuine three-season use across the UK and most of Europe. The 850 fill power is genuine expedition-grade loft in a bag that costs under £220 - a price point where most competitors are still using 650 to 700 fill. The DWR-treated down is a practical consideration for wild camping in the British uplands where condensation and damp bivvy bags are the norm rather than the exception.
Construction details are solid rather than flashy. The outer shell uses a recycled ripstop that packs tightly without the crinkle noise of cheaper fabrics. An anti-snag panel runs the length of the YKK zip. It stuffs into a dry bag rather than a compression sack - better for long-term loft.
Packed size is 19 by 14 centimetres, smaller than a 1-litre water bottle. For anyone counting grams on a multiday route, that packs-to-warmth ratio is competitive with bags at twice the price from larger brands.
Alpkit is a B Corp and designs in-house in Nottingham. The Pipedream 400 consistently sells out on restocks. Worth buying when you see it in stock.