4" bolts not as pictured
The longer ("4") version of these bolts do not have the fluting that is pictured on the shafts of the shorter bolts. That may or may not effect the tightening of these bolts when installed. I'll find out when I get to that stage of my build. Other than that, they appear to be a good quality bolt & nut at a very reasonable price.
Casket Builder Supply
These bolts are designed for wagon wheels to secure the steel "tire" to the wooden wheel. We find the larger bolt does not need the same fluting as the smaller bolt. I supposed the Wheelrights sorted this out a century ago! ;-)
Ordered the 4” bolts they did not have the spirial on the top, did have the big heads There were some problems with them turning dining installation assume this was due to the lack of spirials.