I have a vision rack.
IMHO the heat cable is junk. It is a fire hazard if you do not route it properly - make sure it NEVER crosses over itself. Problem with crossing itself - the insulation melts, and it shorts. Then you have a fire.
It needs to be controlled with a quality thermostat.
I opted not to use the heat cable. Instead, I snaked flexwatt heat tape through the rack - two rows of 3" tape (I use the rack for 32 quart tubs).
First put down aluminum foil tape (kind they sell at bean farm) so that flexwatt is not directly on the plastic. Then snake flexwatt through - and cover the flexwatt where the racks will sit on it with another layer of foil tape.
Then use a quality proportional thermostat (like a Helix DBS 1000) to control the heat tape.
Works very well for me.
IMHO they don't provide enough heat cable to do a full size rack anyway, and I sure as hell wasn't going to buy more.
eBay the heat cable, someone will buy it.
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3.5 L. getula californiae
1.1 L. getula nigrita
1.0 Boa constrictor constrictor (suriname, fostering/rescue)
2.3 Elgaria multicarinata multicarinata