Like the one below: doesn't hurt to bury a spare in the floor. I'm pretty sure this works with Schluter and others. Not required for my project. I'm not 100% sure but I believe this is 12000 Ohm. New, never used.

https://www.gescan.com/products/17-heat-and-ventilation/06-electric-heating/04-floor-warming/02-controls-accessories/p-TlVIQUMwMDA4-nvent-thermal-ac0008-nuheat-probe-floor-sensing
When you call please mention you found this ad listing on OKz.ca