The gauges on these strings are the same as other (considerably more expensive) string manufacturers for the needs of 8-string guitars. However, the way I use them is not use the first and last string and use the 13-64 as baritone gauges on a 6-string guitar. They are perfect since they have slightly more tension than other sets which are meant for baritone, meaning you will not have loose strings, therefore tuning issues (try a .064 on a slightly better tuner to see how much it jumps from sharp to flat if there is not enough tension). The other great advantage is this is the first affordable set that allows you to do this, meaning you can use it as a standard set, change it more often if you feel like it (or keep one as backup) and not worry too much about the cost. All I see with this set is win-win all around.
