Each strip has a green tape (the red line) applied to the inside face. This tape is a silicone bond-breaker. The silicone will not bond to this part of the strip.

The silicone only bonds to the upper part of the strip at X and the ledge at Y. To accommodate joint movement the silicone releases off the green tape and stretches like an elastic band to create a flexible bridge between the strip at x and the ledge at y.

This ‘bond-breaker’ tape creates great flexibility in the silicone, the ‘shielding’ effect of the strip over the silicone promotes durability and hygiene in the shower environment.