I have tried a Dawei Sprungfeder G3 (A2 sponge , now not anymore allowed by ITTF just because Dawei didn't want to pay to be on the ITTF list of approved rubbers).
I have a 1,8 mm black rubber, it is a very capable and fast rubber (more speed and spin than a Sriver L), but has got a HARD sponge...