These are pretty small (look at the list of what's available in the description. Or you can make your own if you have a milling machine. Just tilt an aluminum block at 45" in your vice...then run a square end mill through it. Instant V-block. It's also possible to make a V-block by clamping two pieces of round stock parallel. Or you can shim too deep a V groove by stacking plates on one side to "raise it up". There are a million ways to get what you want.