Barrier Layer: High Melt Film
Adhesive Layer: Low Melt Film

Seam Tape is applied with a hot air welding machine over previously sewn seam to prevent leaking water, air or any other substance through the stitch holes.

When to use a 3 layer seam tape:
3 layer seam tapes are typically used when seam sealing a 3 layer fabric.  The fabric layer of the seam tape is designed to match the tricot liner of the fabric.