Now that I know what a polyswitch is and what it does, and how it works I am wondering. I have read the other threads that allude to this part and most of the advice it to remove and install a jumper. The thing that I wonder with the original tweeters no longer made wouldn't it be a good idea to do what ever you can to protect the original if you have them. I am not sure what the value is on the installed MCI-500 but the 500 number on the ones I checked on means 5.0 Amps. The part is $1.70 at Mouser wouldn't this be cheap insurance? If you look at the schematics for the Model 10 the earliest one has no protection, the 2nd generation XO has a fuse, after that a polyswitch called safetyguard. What is the consensus out there. The biggest problem can I see is will there be room to install one with the beer keg sized capacitors that will be installed.