The Fulltone ETC-1 is a Replacement Tape Cartridge for the Fulltone Tube Tape Echo delay boxes. I don't think that they can be used to fill other real tape delay effects, as they are specifically designed for the Tube Tape Echo. For those who want to know more about the Tube Tape Echo, you can check out my review of it on my page, but it's one of my favorite delay devices period. It simply sounds awesome. These tapes are to replace the tape inside of it that will wear out after a certain period of time, of which length I'm not 100% sure about, but some seem to wear out faster than others. While I don't own a Tube Tape Echo, one of the studio that I work out of has it and I know that they've had some trouble with these tapes recently, as they're wearing out way quicker than they should. I'm not sure if anyone else has this problem with these, as perhaps it could be a slight issue with the Tube Tape Echo itself, although while the tape was on, there were no audible problems. To make matters worse, I think that Fulltone has stopped making these tapes, although I'm not 100% sure on this. Either way, they are difficult to find now and at the very least they are on back order if you try to get one online. This is of course a major issue that I'm sure Fulltone will address. Hopefully not too many people out there are having the same problems with these tapes, and if they are Fulltone does something to fix the situation or at least start issuing more tapes. Tube Tape Echo owners will definitely want to keep a close eye on this situation and see how it plays out as it could be a problem going forward if you're planning on using your Tube Tape Echo for years to come.