As Dwyn wrote for the website section on Twins:
"A new two-hole seedbead. It looks a little like those domino masks for a maskerade party - but with two holes, there are many, many new possibilities for new designs.
Actually I should explain here that there are two very similar beads that are small, oval beads with two holes in them. We have both the Twins and the Superduos. The difference is the Superduos are more exactingly made, and a little more substantial - they are a little heavier. And, as such, a little more expensive than their plainer cousins - the Twins. The Superduos also come in some more interesting finishes and colour variations. If you think that is confusing - well, you are in good company."
Thanks to Jennifer VanBenschoten, editor of Beading Daily, for explaining the difference in the manufacturing of the beads.
"SuperDuo seed beads are pressed glass beads, meaning that they are made in a mold so that each bead is highly consistent in shape and size. Twin seed beads, on the other hand, are manufactured according to traditional Czech seed bead making techniques where the beads are drawn, cut, and tumbled, resulting in a more variable shape and size."http://www.beadingdaily.com/blogs/beading_supplies_we_love/archive/2012/06/25/superduos-vs-twin-seed-beads-which-do-you-prefer.aspx
I realized there was a definite difference in size when I started designing a bracelet using twins in a right angle weave stitch. The SuperDuos are definitely bigger and created a larger space between the RAW units than the Twin seedbeads did. I had to add in some 15/0 seedbeads when using the SuperDuos with 4mm Swarovski Crystal pearls and bicones in 4mm. So they are not totally interchangeable. If a pattern calls for one or the other, choose wisely unless you want to start making adjustments to the pattern.
I made the green bracelet with SuperDuo's, 2.5mm Swarovski Crystal bicones and size 15/0 seedbeads.
The purple bracelet is made with SuperDuo's, 4 mm Swarovski bicones in Crystal Golden Shadow and 15/0 Charlottes in Bronze (tb15r221).
The black and silver bracelet is made with Twins, 4mm Swarovski Crystal bicones and pearls with 15/0 seedbeads.
You can see that I had to add in the 15/0 Charlottes for the purple bracelet in between the bicones. Maybe if I didn't add the Charlottes in the RAW unit, I wouldn't have needed to add them in with the crystals. Designing is all about trial and error and working through variations until what you make looks like the picture in your head!
Preciosa has some really nice patterns using the Twin beads on their website if you want some free patterns.
Have you made anything with them yet? Let us know by leaving a comment below.