They can make any size actually, not just the listed ones, as long as it fits the BCD of course.
Expensive, but really nice rings.
E-mail Brett: he'll respond asap I'm sure.
On a 50/38, the weight of an outer road ring is around 80g and the middle would be around 32g.
How much can you save on the FSA superlight crank with 53/39 when you replace the chainrings with Boone Titanium Chainrings?
How many kilometers can you make on them?
As far as weight, the Boone with SRP or tune chainring bolts would weigh +/- 122g (80 + 32 + 10). I don't know what the FSA rings/bolts weigh (I will weigh this weekend because I am interested), but Tiso would be +/- 144g, Campa would be +/- 160g, so you would be looking at between 22 and 38g savings I presume; if the FSA rings weigh more than Campa even more weight savings then.
As far as durability, I think the titanium will be very durable, people write that they ride them forever.
Here's a quote from Boone for those running Campa 10 drivetrain (when I was asking about making a Campagnolo-compatible compact crankset):
"To make them compatible with campy 10 speed I have to mill .5 mm off the backside of the chainring to set the two rings closer together. It would be nice if campy offered a thinner spider instead of milling the back of the ring, but I guess they would rather have compatability with all spiders and use a special ring. Since that is the case, any 110mm will work fine. The few guys I have made these 10sp rings for were using FSA cranks, and they were pleased with the results. Let me know when you get ready or have any other questions.