In the R-390, R-390A and R-392, all should be #10. In the R-391, each autotune has one #11 adjusting screw. When field replacements are done, other screws may have been used. I found #11's in an R-392 that I worked on, for example, as well as allen screws. Paul On Thu, 7 Aug 2003, RJ Mattson wrote: > What size bristo wrenches are encountered in Collins equipment? > bob...w2ami