As you've probably gathered from reading our string descriptions, the selection of string can make a profound difference in response, so D'Addario offers strings in three flavors: Orchestra, Hybrid, and Pizzicato.
The Helicore Hybrid are a purposeful compromise between the extremes of their Orchestral and Pizzicato strings. While the orchestra strings are designed primarily for Arco (bowing) and the Pizzicato strings are primarily for those playing pizz (plucking), the Hybrids are made for those who happen to do a little of each! They have slightly more growl and sustain, and are not quite as bowable as the Orchestra set -- but still are quite a nice choice if you bow sometimes, but want a bit more grit and sustain than the Orchestral strings provide when playing pizz.
Bottom line: They make for a very good "all around" crossover sort of string for those who play in a variety of styles.
They are available in 1/2 sizes, and also come in light, medium and heavy tensions.
An Extended E/C string (for low string extensions) and a Low B string are also available in 3/4 size.
We are sorry to hear of your experience. If you experience a problem with your strings (or string set), you may contact us (D'Addario) to see whether a manufacturing mishap is the cause. If you wish to return the string(s), visit http://www.daddario.com/ra. Please return the string or set in question in its original packaging (including corrosion intercept bag if possible). This will help us determine if a defect or other malfunction has occurred. Upon receipt and evaluation, if a manufacturing defect is revealed, we will quickly send you a replacement.
NOTE: Though it may not be the case in your situation, please keep in mind that premature string breakage is often caused by burrs or rough edges that develop at the nut or bridge/saddle. These rough edges are often difficult to see, but can be ruthless on strings. If your string continuously breaks at the nut or bridge, please check these points of contact for a nice, smooth surface. If burrs or rough edges are found, contact your local music shop or luthier to perform the necessary minor repair to resolve this common problem.