G'day Darren.

Thanks for getting in touch, it's pretty hard to give you an accurate idea of the correct size to chose without being able to see the sleeping bag you have. We'd suggest checking the dimensions of the bag the sleeping bags are currently in and choosing based on that. I would say you'd need at least a 20L or 35L Dry Sack depending on whether the bag in synthetic or down. If you select the size in the drop-down menu it will give you the in-use dimensions so you should be able to choose based on this.

G'day Brett,

The Ultra-sil 35L dry sack has a 35L capacity. The in-use dimension length of 70cm is when the bag isn't rolled down. Once you roll the top over a few times it will reduce the total length by a few centimetres.

G'day Gabrielle,

It's hard to say as different types of down jackets, and exterior materials will compact down to different sizes. It might be best to pop in to try and compact it into a ziplock bag or similar so you can get an idea of the compressed volume, and therefore size of Lightweight Dry Sack.

G'day Michelle,

I've tried to do a bit of research for you on the shop floor and here is what I've come up with. The 8L sack will fit the Sea to Summit SI Comfort Lite the best. I personally believe the 4L would just be too tight. I'd also recommend the 8L sack for your sleeping bag although you may have to stuff it in. This is a bit harder to gauge though without seeing the bag itself. Working with all this, a 20L sack would be best suited to fit both. I've worked on the basis that it's always best to go bigger than smaller with dry backs as you can always roll the top a few extra times.