They aren't enclosed. I have a pr. of them laying in front of me. The heating element is in the blade itself, wire plugs right into the end of the blade. Take the wire off, and they look like a regular blade. I have talked to truckers that swear by them. The replacement blades aren't bad either, 5. 00 ea. , and have a 3yr warrenty. Hope we don't need them, but will find out this winter.
Ordered them from Geno's, a local glass shop here was selling them for 69. 00 a pr.
Larry