The name is very clever; vString starts with "vS" (Violet Studios), and includes "string", alluding to polypropylene or "string" breast implants that the FDA banned in 2001. A very few women still have them, most notably Chelsea Charms, and I believe her look influenced the look of vStrings.
vString prim breasts give you many options. There are two HUDs. In practice, I think that the one that lets you change size and some other things will be rarely used. It's far easier to simply touch the breasts and call up a popup menu that gives ready access to that HUD's functionality and much more--but not to positioning the breasts on your torso; that is left to the standard Second Life editing options, which are easy to use, so why reinvent the wheel? The other HUD is the "Breast Look Designer", which gives you control over skin and tinting for various aspects of the breasts and of the bra and tank top layers. vString breasts are made to work very easily with Violet Studios skins; as the docs say,
If you own one of our Verotic Human Skins, or Demon, or LTX range prior to the release of the vStrings, simply go in to the appliers folder for your skins, find the updater and wear it. A new version of the appliers will be sent to you, including the new vString appliers.Speaking of size: you can control the size of nipples as well as the breasts as a whole, and in addition to discrete jumps in size, you can start ongoing growth and stop it later.
There are a lot of options for "interactivity", i.e. whether and how up to ten other people can modify the state of your breasts. You can either permit it or not, and modify the set of people you grant permission to.
So, how do they look? I first tried them with a turtleneck that I have worn for a while:
Of course, I wouldn't stay at that size. (Besides, one effect of actual string breast implants is that, barring draining of the fluid that the polypropylene string absorbs and irritates surrounding tissue into producing, they will make the breasts continually grow.) Here you can see that these prim breasts, like some others, come together at the top at a point over the sternum, so they can be pushed to very large size.
Finally, I had to try Bad Kitty's gorgeously detailed "Tied Up" top. Here you see what's a problem with all prim breasts: tops with a neckline are just about impossible to match up where the clothing layer joins the neckline. (UPDATE: and you can see that that meeting point, which the clothing layer has to be set up to cover, is at the very top of the sternum as I have them positioned. That may be a mistake on my part.)
vString prim breasts are, as I write, L$1000, with free updates for (second :) life. The makers encourage feedback, though they admirably say "we don't do promises". The shape one prefers is a personal choice, of course, but given the features and openness to suggestions, I think that people will be very satisfied with vString prim breasts.