The Al Cass flugel horn mouthpieces actually fall under his patent classified as "doublers", they have his trumpet rim. They are not traditional flugelhorn mouthpieces.

The most common sizes are the flugel 3,4,5,6 and 3s,4s,5s,6s. The 3 and 4 have C cups and the 5 and 6 have V shape cups, the 6 being the deepest. The "S"
versions have a curved inner rim which makes them feel smaller, hence you could assume the "S" stands for "smaller" though it is not exactly known the meaning of the "S".

s vs non-s. From comparing both side by side, what I have come to believe is the s has an inner curve/bite, where the non-s seems to be "straight out", no curve on the inner rim. I would guestimate the s is smaller than the non-s. (most likely because of that curve) That brings another question, because my father was such a fan of "simplicity", does the "s" simply mean "smaller" ?

I have looked through his personal notes, what he wrote down, but I don't think he wrote everything down. Most of the notes were pertaining mostly to who used what. Notes on individual custom work etc.

I also believe (as far as the flugels go), the 1 and 2 flugels were the 1st ones developed. Then starting with the 3 size, the "s" began, the 1 and 2 were dropped and continued with the 3,4,5 and 6. All of these have the "s" variation. On a market note, these flugels have been HOT. I have received more requests for flugel's than trumpet pieces the past year.

I've tried to measure these in the past with a micrometer but it's not that easy. Even when comparing side by side because you lose the place from where you started your measurement due to the curve of the rim. That is when I believe Brad came in and said "they are all the same!" I'm glad he came out with this theory because I was losing my mind and rightfully so, trying to measure, expecting a difference and not finding one. I believe it's so small a measurements, in the 1000ths.

 to compare the cups. Left to right...4S, 4, 7S M ( in the middle) 6s , 6

The 7SM (in the middle) is a cup c, looks ALMOST the same as the 6s and 4s.

Al Cass Flugelhorn! Prototype model 7-S, simply inscribed "7-S   M". has a C shape cup.  Does the S mean "symphony" like on the trumpet pieces? Does the M mean "model" or "Mellophone?" It looks to be the size of a Flugel so the M may indicate "model". "M" was seen on pieces marked "model" I believe this is a FLUGELHORN MODEL. Again, this is a developmental piece so possibly mis-understood if one just goes by the model#.

The famous Trumpet rim to FLUGELHORN #3

Just comparing the outside of the 3 and the 7.They look very close in size, even the cup.the 7SM is a prototype. The later 7 had the V cup., but this one a c cup.


Al Cass Flugelhorn! Prototype model 4-S, simply inscribed "4-S". has a C shape cup. Does the S mean "symphony" like on the trumpet pieces?
Al Cass Flugelhorn! Prototype model 4, simply inscribed "4". has a V shape cup similar to that Art Farmer used! Later model 4's had C shape cups. This appears to me to resemble more of the later model 5, 6 or 7 Al Cass flugel!
Al Cass Flugelhorn! Prototype model 6-S! C cup Simply inscribed "6-S" However resembles, to me, more the later model 3 or 4 flugel!
Al Cass Flugelhorn! Prototype model 6. To me, This resembles very much the piece used by Art Farmer! Has the V shape cup
Art Farmer played an Al Cass flugel....this one is the FARMER  ! ! !
A MORE RECENT 3S c cup Model