RAB assign the INFINITY name to its leading edge down products, designed to be very low weight - for example the Infinity jacket is our lowest weight down jacket with a full hood and 210grams of down.
In the same way the Inifinity sleeping bags offer their particular performance ratings at a very low weight - making them very competetive. The Inifinity 300 is our lightest bag rated down to -2C.
There are only so many ways you can improve a down bag or make it lighter - RAB have looked at all aspects and not compromised features, the Inifinity 300:
Where RAB could have compromised but hasn't:
In use I found the bag to be really good, the slight compromise on the zip length went unnoticed until I wrote this review and even though I'm a biggish person I didn't feel the bag restricted me in any way.
The zipper worked well and when required the hood give good coverage when the drawcord was pulled tight. RAB should know a thing or two about sleeping bags and this is their self confessed lightest bag with a minus 2 rating, aimed at backpacking, adventure racing and fast&light mountaineering.
Its most direct competitor is the Wetsern Mountaineering Summerlite, which is lighter but only gets a 0C rating. The Inifinity 300 therefore would suit anyone wanting a bit more insulation but still wants to keep weight at the minimum.