Was looking for a sharpening rod for a Bosch multi-tooth rotary hammer and this was found. That's not a spline, it's an eighth of a hexagon. Luckily I have a Bosch Brute Hammer that can use this tool.
Just received it today and have not used it yet but am very pleased with the flesh this thing ! How well it clogs the rebar now depends on the punch. Remember this is for 11/8 hex and not the SDS driver.
I use it with a Hitachi electric jackhammer. I bought it to drive in a couple of ground rods but have also found it useful in the garden for driving 4 foot lengths of old 1-1/2 inch diameter steel pipe into the ground, around 2 x 12 lumber and railroad ties to support for slope terraces. What would have taken me a day if I could have done it with a sledgehammer was done in San Diego in 15 minutes in clay and river rock.