What is most ultralight belt?

If you've got a local source for strapping and buckles, make one yourself. I've found that it's the best way to get exactly what I want. If the belting is too soft it tends to fold up when tightened. It's hard to find a commercial, nylon webbing belt, that has all of your desired features. It's easier to find a good backpack.

Fortunately there are good sources in Berkeley, where I can get to them.

Probably Spectra cord with a cord toggle to tighten it. Similar to the BPL Thoroghfare pants. I like this set up.

I removed one from some Royal Robbins pants nmiller08 gave me. It uses the same buckle as a pair of Mountain Hardwear pants I have. (It is not the buckle in your picture.)

The belt is yours. It should go up to about a 40" waist.

Ah, Nick-
So heavy! Just a piece of Spectra cord with a slipknot in a trucker's hitch!

I made a belt from a leftover toggle thingie and a thin piece of elastic cordage. I have to slip on my pants with the belt fastened, but I left a lot of extra cordage to allow for that. Not as light as spectra cord with a fancy knot, but being able to whip your pants off in a flash can be useful if you really have to go.

Lately I've been harvesting webbing and fasteners from stuff at the thrift store.

I just got this belt:

http://www.strapworks.com/Sports_Belt_p/sbpc34l.htm

Sports Belt 3/4" w/ Nylon Cam Buckle & Lightweight Polypropylene

it is only .7 oz heavy, very light. I wanted this to tie my cuben fiber parcho tight around the waist when not using it with a pack. My other belt is sewn into my hiking pants.

And this belt is 61" long, I can cut it shorter bringing the weight probably down to .55 oz.

With shipping the belt was less than $10.

"I made a belt from a leftover toggle thingie and a thin piece of elastic cordage. I have to slip on my pants with the belt fastened, but I left a lot of extra cordage to allow for that. Not as light as spectra cord with a fancy knot, but being able to whip your pants off in a flash can be useful if you really have to go."

Diane –

Add a mini biner. Let the toggle catch in the narrow end and attach the biner to a loop on the other end of the cord. Now you can use the toggle to tighten the belt and in a flash you can undo the belt by unclipping the biner or sliding the toggle away from the narrow part of the biner. You are 95% there :)