Hi,
Unit of measurement or your measurement unit- you are maintaining for material master not for Material Group.
Material Group does not have any controlling features where Material Group is only used for reporting purpose& can restrict the scope of analyses and can search material master records with search help.Material Group is a key that is used to group together several materials or services with the similar attributes.
Each Material or Service is assigned to a particular material group during creation of master data.
NOTE:
If you are using for service procurement,then can set Unit of measurement,Material Group as default value during service PR or service PO creation by activating Unit of measurement,Material Group in t.code: ML91.
Regards,
Biju K