Originally Posted by
soyabean
11-30T is practically a mtb cassette.
It's a normal road cassette, the same as Ultegra 11-32, and on 12s 11-34 ....
105/Ultegra rear mech with medium cage works well with 11-32 cassette as well, just avoid maximum cross chain (Di2 will block it for you - small/small - so no full slack situation and risk of dropped chain, however big/big is allowed (as an emergency I guess, or if you miss gears) )
(MTBs cassettes are from 42 up now
)