diff --git a/src/lib.rs b/src/lib.rs
index 03e746e..bd6f23e 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -2,9 +2,12 @@
 // #![no_std]
 
 #[allow(non_camel_case_types)]
-pub type U3076 = <heapless::consts::U2048 as core::ops::Add<heapless::consts::U1024>>::Output;
+pub type U3072 = <heapless::consts::U2048 as core::ops::Add<heapless::consts::U1024>>::Output;
 #[allow(non_camel_case_types)]
-pub type MAX_COMMAND_DATA = U3076;
+pub type MAX_COMMAND_DATA = U3072;
+
+// 7816-4, 8.2.1.2
+pub type Aid = heapless::ByteBuf<heapless::consts::U16>;
 
 pub mod command;
 pub mod response;