"One bag that's stood out over the last two years has been the tiny K Filler sleeping bag. I've used the bag a lot, both as a bag in its own right, both as a stand-alone bag but also as a 'sheet' style bag in hostels and grotty hotel beds (good for keeping the bed bugs out), as well as a liner bag in both down and synthetic bags. One way the K bag works so well is that it both insulates as well as reduces convection inside the bag, filling in the dead air space. Sleeping in the desert can often see you feeling very hot when the sun goes down but shivering at 3 am. And so I would often go to sleep with the bag around my knees and slowly pull it up as the night went on."
— Andy Kirkpatrick. Read full review
"A genius idea."
— Trail Running Magazine.
"On a couple of occasions, faced with frigid temperatures, I've tried stuffing two sleeping bags together. Sadly, it's a fix that never works! The size mismatch always leads to compressed insulation and more cold spots than you can shake a stick at. PHD, with some neat design tricks, have cracked this problem and, in the process, come up with a highly flexible sleep system. As well as allowing sleeping bag layering, the system also takes into account other down clothing. Basically, you have a main sleeping bag which is size-matched to an inner bag. You can pick and choose for the main sleeping bag. This is then paired with an Filler Bag that can then either be used on its own as an uber-light summer bag (packs up not much bigger than my first), or can be paired with the main bag to boost the overall rating by a good 10 deg C. So, for me, the system works like this: paired bags for deep winter, solo main bag for the rest of the year, and then the inner for ultra-light trips at the height of summer. Verdict: An investment in flawless design that will last and last."
— Jeremy Ashcroft, Mountaineering Editor, Trail Magazine
"I have a long-held belief in the 'layering principle' extending into sleeping bags. PHD's bags suit a multitude of adventure activity situations including:
- Expedition sea kayaking
- Himalayan style trekking where you travel through a wide range of temperature zones
- Cycle touring where there is a similar packing issue to sea kayaking and potential for travelling through temperature zones
- Plus, anyone who needs to use their sleeping bag across seasons. E.g. Just 'layer up' to convert your summer bag into a 'winter warmer'
During recent sea kayak expeditions in Greenland, my PHD Minim Overbag
, and Filler
bags were tested in temperatures ranging from just above freezing to as low as -10°C. It is a pleasure, when you know the temperature is dropping, just to slip into another bag and double the warmth factor"
— Sam Cook
"I used the Filler Bag in the Alps with great success. I happily slept in it, albeit with a vest and hat on, at temperatures down to around 12 degrees C and was perfectly comfortable. Saved a lot of pack weight. Thanks for a great product, the down you use is obviously of a very high quality."
— Mike Jones.
""I 'bivvied' in the snow on the fell above my house. Inside a bivvy bag I was as 'snug as a bug' in the Minim Overbag and Filler. So much so that I slept until 8am. The temperature dropped to about -6°C."
"PHD has reminded us once again why it is one of the world's best manufacturers of lightweight gear with the release of its super-light 240g Filler Bag. When used inside a sleeping bag, the Filler is designed to expand in the unused space and cut off convection currents to add 10C of warmth. It can be compressed into an impressively small size zero PHD stuff sac (10x18cm)."
— TGO Magazine.