Feature:
Purchase a variety of grades for compression. I wish you could purchase these at more local shops for a decent price. I wish you could purchase mixed hardness sets for a variety and a price break. I wish it had the wattage capability for the tube set you buy.

Quality:
Great guarantee, best in the business period! Product in perfect condition each time you get them.

Value:
Compared to the new old stock, you are really just paying for warranty, service and consistent quality grading. Most of the tubes are made in russian and china, they are tightly tested and graded so the customer does not take a risk.. GREAT IDEA!!

Desirability:
Great look, everything about a tube you could want labeling is perfect, it shows the quality dedication to the actual product.

Sound:
It sounds just like it was graded to be. It will never be an RCA BLACK PLATE or an old 5881 because it can't. Good for old rock sounds. I use Fender Twin reverb 1973 and a 1484 Silvertone Twin Twelve 1965 Not sure of what will make it better but the system works on grading and that is all it supposed to do and give you better and more consistent reliability and it DOES just that!

Support:
GT is the best to deal with when it comes to tube purchases period. No JUNK ALLOWED the others are I hope I get lucky and get a good set and hope they last and sound good. With Groove you know what you are getting.

Overall:
Wish I had a brochure of all the products so I would know what other products I could purchase