This is a front dropout spacer for a standard 100mm spaced bike fork. It's used during shipping to protect the fork from damage.
When you ship a complete bicycle, you generally remove the front wheel and install a dropout spacer in the fork. When shipping a frameset that hasn't been built up, you use dropout spacers in both front and rear dropouts. This model is for just the fork, and is spaced to fit most road/hybrid/cyclocross forks, plus all mountain fork that take standard QR axles.
I spaced the dropout insert part at 10mm to start, which will be a bit of a snug fit on most forks.
12.5 w x
2.86 d x
4.921 w x
1.126 d x