Differences between A caliper & S caliper rebuild kit

[HKZ Bob]

Dear Forum,

who can tell me the differences between the ATE A caliper rebuild kit and the S caliper rebuild kit.

Here some numbers

S caliper rebuild kit 901 351 998 00 ATE 13.0441-4806.2
A caliper rebuild kit 911 351 946 00 ATE 13.0441-4819.2

Both use the same dust cap 13.8102-4801.1 and have 48mm pistons
The front end design is different.
Who can help?

BR
Bob