Purchased to use with GM-800. To anyone thinking about buying, read the manual and watch the setup videos first. When everything is set up properly, it works incredibly well with the GM-800 even on the low strings. Any issues with glitching or tracking will be down to sensitivity settings, GK5-B pickup location and playing style. I've used various bass to midi devices over the years, and the GK5-B with the GM-800 is a seriously creative combination. Ensure you understand how the GK5-B works before you purchase it, and remember it needs to connect via the Boss serial GK cable to a compatible device. I play fingerstyle and this gives a lot of control very easily, particularly for keeping strings muted. I'd recommend trying the GK5-B on different basses and in different positions (use some temporary tape rather than the included tape) and give yourself time to experiment with the various configuration options. If you take your time and adapt your playing style to keep tracking accurate, this is a seriously worthwhile investment and opens up amazing opportunities for the bass guitar. Yes, it takes some work, but the results are amazing. Highly recommended.