This product is either discontinued or we cannot get that from suppliers.
D-LINK DXS-3600-EM-4QXS 4-Port 40g Qsfp+ Module, Expansion Slots-4, Expansion Slot QSFP+.
The DXS-3600-EM-4QXS expansion module provides an additional four (4) 40Gbps ports for the DXS-3600-16S and DXS-3600-32S managed switches.