I bought one of those laser cut sets a few shows back though I've never used them. But I asked whether they were BA or metric and they said it didn't matter as the metric sizes would fit close BA nuts. I found this table somewhere, may be useful.
Number BA
|
BA spanner size across flats in decimal inches.
|
Metric equivalent
|
10BA
|
.117 inches.
|
2.97mm
|
9BA
|
.131 inches
|
3.33 mm
|
8BA
|
.152 inches
|
3.86mm
|
7BA
|
.172 inches
|
4.37mm
|
6BA
|
.193 inches
|
4.90mm
|
5BA
|
.220 inches
|
5.59mm
|
4BA
|
.248 inches
|
6.30mm
|
3BA
|
.282 inches
|
7.16mm
|
2BA
|
.324 inches (Probably the most commonly used BA size)
|
8.23mm
|
1BA
|
.365 inches
|
9.27mm
|
0BA
|
.413 inches
|
10.49mm.
|
After all it doesn't matter what size is stamped on the spanner, only whether it fits well enough to be able to apply the desired torque without taking the corners off the nut.