Once the parts arrived, turns out the parts received were incorrect.
I shipped the parts back via USPS delivery confirmation. According to USPS, Miller received the parts back on August 23.
To date (six weeks later) I have not received a credit back to my credit card. No response from Miller on my email requesting a credit. Spoke to Miller last week, was advised "someone would call me back shortly". I'm still waiting on the phone call.
I'm done with these people. The charge has been disputed with my credit card company.