Cisco C3850-NM-2-10G Catalyst 3850 2 x 10GE Network Module.
This module has four slots:
Two slots (left side) support only 1 G SFP modules and two slots (right side) support either 1 G SFP or 10 G SFP modules.
This is supported on the following switch models:
In the C3850-NM-2-10G module, the first two parts are natively 1-G ports and the last two ports are natively 10-G ports. So, you configure the 1-G posts as GigabitEthernet1/1/1 through GigabitEthernet1/1/2, and configure the last two ports as TenGigabitEthernet1/1/3 through TenGigabitEthernet1/1/4, even when you are operating the last two ports as 1-G. Only four interfaces are valid, and the other four should not be used even though they still show up in the CLI.