[wendbill]

I have a vague idea that small boro is considered up to about an inch, but I think I'm guessing.

It may be worthwhile checking the torch section to see what info is available.

I'm using a minor burner with an Airsep 5 LPM concentrator. The one time I tried to melt any boro on mine I concluded my attention span probably wasn't going to be long enough.

I don't think anyone has ever regretted the decision to have more oxygen available.

Here in Oz though, oxygen tanks are prohibitively expensive, so most use concentrators.

At the time I bought mine, it was a case of waiting for the occasional concentrator to come up on ebay. Now one of the local lampwork suppliers imports them from China.