Divergent discs says about their new disc release the Alpas:
"The Alpas is a thin profile disc (1.9cm) with a completely flat top. It is stiff enough to be thrown comfortably but flexible enough that upon impact it collapses and stays put.
Unlike our other discs made of thermoplastic polyurethane, the Alpas is made compressing silicone polymers. This process allows us to use a variety of mixed color patterns."