QSFP28 is a "quad SFP28" which means four channels of 25Gbps combined to 100 Gigabit Ethernet. The form factor is equal to QSFP+ which makes it possible for equipment supporting one also can support the other. This simplifies the transition from 40G to 100G.
The fields for product selector/filter have now been moved up to the left. Tick the desired criteria to narrow down the selection. In the end, you will be left with the transceiver(s) best suited to your needs.