Your Hispar 500 was fine on Kilimanjaro. If you add the Hispar Overbag, the double bag will take you up Everest. And you still have two different bags to use separately in warmer places. The versatility of the Overbag needs no further comment.
Of course combining bags is also about economics. When you are moving up the expedition scale, you need better gear at each level, and it can be frustrating not to be able to use the perfectly good sleeping bag you already have.
One option is to go ahead and buy exactly the item you need for the next level: this will provide you with the lightest, most efficient bag for the expedition, as long as you can afford it.
The cheaper option is to look at the Hispar Overbag. It is cut to fit over the Hispar 400, 500 or 600 and will add about 24°C of insulation to the inner bag (see examples below). It will also accommodate a 500 or 700 bag from our Baltoro or Diamir ranges.
The fill in the Overbag is our 950 down and with Drishell outer and MX inner it lines up with our other Hispar bags in the superlight expedition category.
Just one last point about this bag. The extra width means that there's room to wear down clothing inside. So as a stand-alone bag it not only offers warmth at –6°C , but you can take it to much lower temperatures with different kinds of down gear inside, even a down suit.
||400 + Overbag:
||500 + Overbag:
||600 + Overbag:
*Typical Operating Temperature (Celsius)
Available in Slim, Wide, and Extra Wide Widths and Extra Long length
This bag is also available in these sizes to accommodate heights up to 7 foot 1 inch (216 cm) and chests up to 56 inches (142 cm). See "What's my size?" for more information.