VELCRO® Brand ALFA-LOK™ Fastener with SilverTape™ 6411. The AFTC Brand SilverTape® 6411 is a high performance double sided acrylic foam adhesive tape. In combination with the ALFA-LOK™ Fastener, this product is suitable for most surfaces, even materials with low surface energy such as ceramics or (powder) coatings. It provides an excellent initial tack and very good adaptability.