There is a bed material called PEI but it is not Kapton, aka Polyemide. It is actually clear and PEI is the brand. That maybe what you got. You can buy 3 inch wide rolls of the Kapton tape on ebay for like 2 dollars a roll. It's much easier to apply then a full sheet. Personally you should use glass and hairspray. It's tried and proven and is much more economical.

I dont like kapton because I always need to reapply it after every use. I dont like the smell of hairspray in my bedroom. My PEI sheet is kind wierd the part stick perfectly fine but when printing the first layer some edges curl even tho the part itself doesnt warp. The bed is perfectly level and Z height is right.