Gear Mods: Osprey Ultralight Stuff Pack Sternum Strap

I really like this little pack. It is super light and stuffs down really small, making it a great pack to carry along when I am basecamping. After setting up camp, this pack comes out and I can use it to carry filters and bottles when I fetch water, or use it as a light summit / day pack, carrying my lunch and the essentials when I am romping away from base.

However, it is about as minimal as it comes and the biggest deficiency is the lack of a sternum strap. I’ve looked at a few other summit packs but the ones that have sternum straps are also generally much heavier. For a while I had just tied a string to either shoulder strap and when I would don the pack I would simply tie the strings together much like you’d tie your shoe. This works well enough, but it’s a hassle.

Some of the Amazon reviews suggest using bed sheet straps, like these:

And I think these would work just fine. But I wanted something a bit lighter, a bit more suited to purpose, and frankly, not to garish.

The Mod

This mod is mostly about assembling the right pieces for the strap. You can readily find an assortment of sternum strap parts. You can even find entire assemblies that would work just fine. I even considered a few, like these:

Of these, the top one, the grey one with the orange whistle, is the best suited. It works pretty well actually, but it just felt too large for such a diminutive pack and at 1.6 oz. it was just too heavy.  Of course, 1.6oz isn’t really heavy at all, is it? But it’s more than 50% of the weight of the entire pack. Surely I can do better than that.

I found it surprisingly difficult to find very small sternum strap parts. I had decided I wanted the strap to be at least 1/2 the width of the sternum straps I had been seeing (usually about 2cm or 3/4″ was the narrowest).  But I did ultimately find just what I was looking for.  Sternum Clip buckles that are 10 mm (less than 1/2″) and would work perfectly with an 8mm webbing. From a shop in Slovenia. Yes, I looked and looked, and literally could only find any other source for these small parts. So, I ordered $1.74 worth of parts and paid $13 to ship to the US. Oh well, if you decide to do this mod and can find another source, please let me know in the comments.

Here’s what you will need:

1 x Sternum Clip:

Micro Sternum Clip

Micro Sternum Clip

1 x Sternum Clip Buckle:

Sternum Clip Buckle

Sternum Clip Buckle

~ 1′ of 8mm Polyester Webbing

8mm Polyester Webbing

8mm Polyester Webbing

There is one small bit of sewing that you must do to secure the webbing to the Sternum Clip (not the buckle).  Simply insert the webbing to the clip and tack in place (hopefully better than I did … don’t press the foot pedal before you have your pieces lined up, lol!).

Sternumclipattached

Sternum Clip Attached

The only left to do now is to weave the other end of the webbing to the Sternum Clip Buckle and then attach the whole thing to the shoulder straps. One thing I really like about this solution is the way these parts clip onto the straps. They’re really intended to clip onto a vertically attached strip of webbing. And I had originally intended to add webbing for that purpose. But then I noticed how well they fit over the hem of the straps I decided to attach them directly to the straps. They hold securely and will even slide up and down for adjustments.

Sternum Buckle Attached to Strap

Sternum Buckle Attached to Strap


Sternum Strap Worn

Completed Strap

And the best part is that it only adds about 5 grams (.17 ounces) to the total pack weight!

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Osprey Ultralight Stuff Pack

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