Elixer Optiweb

I've never seen this type of Elixer string before. I clicked on the TB banner ad and saw this:
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Special lightweight coating offers more natural, familiar feel.

Thanks to Elixir's OPTIWEB Coating, these nickel-plated steel electric guitar strings give you the performance of a natural string—that crisp tone, natural feel and playable grip you know and love—without sacrificing the signature long-lasting tone life of Elixir Strings. Compared to their POLYWEB Coating and NANOWEB Coating, the OPTIWEB Coating offers their most natural and familiar feel. This lightweight coating allows the string to vibrate with less damping, while also having a firm grip, putting you in control of bends, vibrato and sustain.

So choose the same premium electric guitar strings that experienced players worldwide trust to keep their incredible tone longer than any other string available. Unlike other string brands, Elixir Strings coats the whole string. This protects not only the outer string surface but also the gaps between the windings where common tone-deadening gunk typically builds up in other brands’ coated and uncoated guitar strings. Anti-Rust Plating on plain steel strings ensures longer tone life for the entire set.

Who wouldn’t love more quality playing time between the hassle and cost of string changes?
For a slicker, gentler feel, try a set of electric guitar strings with their POLYWEB Coating, which also feature our warmest tone. Meanwhile, their NANOWEB coated strings sound bright and feel smooth, striking a dynamic balance between POLYWEB Coating and OPTIWEB Coating.
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The ad was for guitar strings. I didn't see bass strings.

 

I wonder why the Optiweb is only abailable for guitar?