Kastaplast keeps it to one formula and its variants. K1 is the premium plastic the whole range is built on, firm with some give and very durable. K1 Soft is the flexier version and the replacement for the retired K2. K3 is the baseline.
K1 Glow, K1 Grind (the recycled version), and K1 Hard are runs of K1 and live on its page.
