these are inexpensive and work perfect with my 4 bolt shimano deore lx 1x9 conversion.
the crank is 3mm thick and my bashrings are just over 2 mm each.
I was able to buy some spacers and make my sandwich chainguide system bulletproof.
I bought these bolts to replace the beat up ones that came with my Truvativ Holzfeller Howitzer crank. They work great as long as your using the original bashring or one that's equally as thick at the mounting points.
Unfortunately I couldn't find a complete size description for this bolt kit anywhere. I found their lengths but that's it. I decided to buy this kit anyway and crossed my fingers.
This is what I found when they arrived: The Nuts are 12.5mm long like they say but they take an M8.5 bolt! Most chainring/bashring bolts and nuts for this application are size M8. I tried to find just one M8.5 replacement bolt online but couldn't. Anyway, you get Four that are M8.5 X 9.5mm long that can only be used with the supplied nuts, and four that are M8 X 8mm long for your granny ring.
Just want to be clear here. You cannot use the M8 granny ring bolts with the supplied nuts. If you strip out the M8.5 bolts or nuts, you'll probably have to buy a whole new bolt kit. If you need to replace a single M8.5 bolt but want to use the same nut, don't even bother looking, it was a waste of time, just buy the bolt kit again.
In the end I decided to buy and use a different bolt kit made by Gamut which comes with red anodized M8 bolts and black M8 X 9.5mm long nuts or black M8 X 10.5mm long nuts. This worked better for me with my aftermarket bashring because it is a little thinner then the original bashring and the red looks nicer too.