Apparently this product has been out for about 6 years. I just found out about it while researching for a tube upgrade and about installing adjustable bias trim pots for my Mesa Boogie Mark 3. These can be retrofitted to any tube amp. Sound like an ideal solution for non adjustable Boogies. I just joined the forum and found no threads on this product thru search. Product originates in UK. I'd think they'd be all over the place now. Anyone use these??