The interior (skin‑contact) side is often medical‑grade silicone or a skin‑safe adhesive gel.

The outer side (facing clothing) could be either matte silicone, thin polyurethane film, or a very fine fabric (to reduce visibility under clothes).

Edges are typically tapered so they lie flat and do not show under clothes.

The reusable adhesive is protected by a backing sheet when not in use to avoid contamination.

Packaging is likely done in clean conditions, with some kind of protective cover or box to maintain hygiene.

They likely do QC checks for size, shape, adhesive strength, skin safety (allergy tests) before shipment.