mysql> CREATE TABLE t (b BINARY(16));
Query OK, 0 rows affected (0.00 sec)

mysql> INSERT INTO t VALUES ('abc  ');
Query OK, 1 row affected (0.00 sec)

mysql> SELECT HEX(b), LENGTH(b) FROM t;
+----------------------------------+-----------+
| HEX(b)                           | LENGTH(b) |
+----------------------------------+-----------+
| 61626320200000000000000000000000 |        16 | 
+----------------------------------+-----------+
1 row in set (0.00 sec)