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Every Part in e-manage has to have a Product Type assigned to it.
When you create a new part in e-manage or import a part(s) from a specifying software the Product Type is set.
Once the parts are added to the BOM for a customer quote the parts are already mapped to the product type which is mapped to the appropriate accounts.
Every part is also connected to a Parts Category which determines if a line item should be taxable or non-taxable
In summary
Parts are Mapped to Vendor REFS
Vendor REFs are Mapped to Product Types
Product Types are mapped to QB Accounts
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