Martyr CMR04AL, Rudder / Trim Tab Disc Anode, Stainless Steel Allen Head, Aluminum, 0.65 L x 5 OD x 0.34 ID

Good aluminum anode. Accurate sizing description. The flat side is pretty flat. I used it to replace a GIANT washer on my sailboat rudder that I lost overboard. I only used half and I machined it to fit but it was a much better deal and in the end better than the original part. It is cast but it machined okay and much cheaper than a piece of aluminum stock.