Why can't I access my custom fields in Rules? What I want:
I want to give my products a weight and I want to calculate the total weight of the order.

What I did:


I'm using Drupal Commerce Kickstart 7.x-2.0.  
I added a field 'weight' to the Product Variation 'Product'.
I created a custom Rule
Added a condition 'Entity is of type': commerce-line-item == commerce_product
Tried also to add or replace the condition above with the conditio 'Entity has field': commerce-line-item has field 'field_weight'
Create a Loop Action for commerce-line-items
Add a Loop Action but don't find the field 'field_weight'


Can someone explain me why I can't access my custom fields in Rules even though I added specific conditions?

Thanks in advance!
You're not looking for the field on the entity you've added it. You added it to the product, so in addition to your "Entity is of type" on the line item, then you need to check the type of the commerce-line-item:commerce-product for whatever product type you're expecting to find the weight field on. Only then will Rules know that that product has that field.