I have a Waste King batch feed with a non-magnetic cover. The cover turns on the disposal by fitting into a notch in the disposal drain when you push down the cover. I prefer it because it is so defined. The magnetic ones seem to need more fiddling with the cover to "catch" the magnet.

Is the Insinkerator cover control plus a magnetic cover?
the Franke? I have chosen the Barclay fireclay apron front sink and I am wondering which batchfeed will work the best with this sink. anyone have a Barclay sink and a batchfeed garbage disposal? Did you need an extension?

I just checked the Franke 3/4 hp batch feed (#FWD75B) user manual from the Franke website. According to the instructions on page 7, it looks to be non-magnetic. You can look up the Insinkerator's manual yourself.

I don't know about the Barclay sink. I recall some threads regarding some brands' fireclay sinks that needed a longer flange due to the thickness of the fireclay. Others don't. Anyway, these flanges are easily found. Of greater concern with a fireclay sink is that you don't over-tighten on the disposal cause you could get crazing.

Why don't you read other threads on the topic of fireclay sinks and disposals on the Kitchens Forum?
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Franke Batch Feed User Manual