Hobby Shops: Is it fair?

[Kcaz25]

I believe a part will fit my car but I am not sure. Often times I call my local hobby shop and have them get parts. They call me when they get in and I drive up and pay for them. Is it okay to have them order a part, determine fitment (i will know by holding it in my hand) and then if it doesn't fit walk away. I would thank them of course.

Is that common practice? Is that acceptable? Should I tell them that I am not sure before they buy it? It is a common part. Could they easily return it?

Thanks,
Zack