F20
F = inner diameter - 5/32" / 4.0 mm
20 = wire gauge - 0.032" / 0.8 mm*
AR = approx 5.1 (F20 ALUM = 5.8*)
*The (bright) aluminum 20ga we use is actually slightly thinner than the other metals, giving the F20 ALUM a larger aspect ratio.

Size F20 has a medium-high aspect ratio. Its AR is very similar to our base metal sizes L18 and D22. Any weave shown here that uses size F20 all by itself will also work if you use L18 or D22 in base metal. Of course the ring counts will be different, but you'll at least know that the weave will work. (Note that L18 has a higher aspect ratio than F20. J18 is much closer...but with L18 you get all the nifty colors of anodized aluminum!)

In terms of 16 gauge base metal, size P16 is fairly close (AR = 5.4), but size O16 will probably be a better match, once we start making that size. In sterling, similar ARs are found in sizes E21, G19, J17 and L16.

1. Create the first row of Japanese 12-in-2, with 4 hanging rings as normal. The difference is that you are alternating sizes: add two large doubled rings, then two of medium rings, then back to the large ones again. Each set still has 4 hanging small rings from it, and an additional 2 small rings connect to the next set of large or medium rings in that row.

If you are creating a reversible bracelet, make sure that when you double the large and medium rings, you add the appropriate color on the correct side.

2. Begin row 2 as normal, by going through 4 hanging rings—2 connecting to a large pair and 2 from a medium pair. It doesn't really matter if you add a new large or a new medium. However, my recommendation is that if you're using a toggle or lobster claw clasp, add a medium ring here. If you're using a slide clasp, add a large set. (See clasp diagrams at end.)

I am adding a toggle, so I also started out with 2 extra small rings on the first set of large rings. Don't worry about them right now, you can add them when you get to the togge. (i just wanted to let you know in case you were wondering why the photo showed extra rings!)

3. Because I'm adding a toggle, I'll use a medium ring here. I'm adding a black one with 2 small hanging rings. Once I close that ring, I'll add a brown medium ring that slides in on top of the black one (because on this side of the weave, the brown and gold rings are on the top.)

4. Once you've added both rings, your piece looks like this. You're now ready to continue row 2 as normal, by going through 6 small (2 from the previous set, plus 4 hanging).

5. Don't forget to add two small hanging rings to that first new large ring. You can scoop the 2 small hanging either before you go through the 6 small rings, or add them after you go through the 6 small, right before you close the large ring. Double the large ring, keeping your color scheme consistent. Your weave should now look like this.

6. Repeat to the end. If you have too much trouble adding the 2 small onto the mediums because there's not enough room for your pliers to get in to close each medium ring, don't fret. You can always do what is shown here: add the medium rings with no hanging rings, and close each one. Then open 2 small rings and add to those mediums. Proceed as normal.

A very easy way to end is simply to attach a slide clasp. It doesn't matter if you end with sets of large or medium rings, but each end needs to have only large or only medium, not a combination. Remove any excess hanging small rings and use D18 base metal or D17 silve to connect to the slide clasp.