This kit is a Grade 8 Stainless Steel ARP (American Racing Products) bellhousing bolt kit for the GM cars with a Bell Housing for the 4L60 or 4L65 transmission. They are not only good looking, and don't rust, but they are super strong for your high horsepower needs and have a polished finish. These bolts have a tensile strength of 170,000 psi. They have a Metric 6 point head and an 18mm, .709 diameter flange for easier access in the tight spots. This kit also includes extra thick heavy duty stainless washers.