You are able to update products from Rectron with Stock Sync. Just choose on Rectron template after choosing to update existing products in your store.
1. Go to Setup New Feed > Choose Update existing products.
2. Choose or search for Rectron template.
3. Once created the template will direct to the feed details page because there is no file setting needed to fill up.
4. If you would like to do any changes in the field mapping section, then you can click Edit settings and go to the second step.
5. If there are no any changes, you can proceed with the Start Process to update the products.
These are the available fields that can be updated for Rectron.