Don't know what year your rv is....but both Suburban & Atwood will void their warranties if used.
That being said....
They work but have drawbacks
1) Have to be installed in drain hole which means they have to be removed every time you drain/flush tank (which needs to be done) so they can be a PITA disconnecting/removing.
2) Very slow recovery time....heating element is only 400W vs OEM element 1400W
3) IF you have a Suburban Brand you are doing away with your anode rod which is a MUST to protect tank. Some of the aftermarket heating kits have a small anode rod BUT OEM rod is 9 1/2" vs the very small rod on end of heating element.
So YES that can be useful but know the limitations/issues
