Defaulting Unit of Measure (UoM)

Hi

I have the following requirement.

We are migrating Product Hierarchies from ECC to CRM 7.0. (only the hierarchies not the Products)

When i create an opportunity in CRM using the Product Category, i need the UoM to be defaulted to "EA".

is it possible to default the UoM for ECC "product Hierarchies"?

Any pointers on this will be really helpful.

regards

Bala