We improved on the menstrual disc concept by making FLEX disc using the latest manufacturing technology and superior materials. FLEX requires different manufacturing tooling than Softdisc and the materials we use in FLEX disc get softer inside of the body when in use. This proprietary blend of materials makes FLEX disc more comfortable for users and helps create a leak-free seal.
That said, both products are still great choices! It all depends on your unique lifestyle and needs.