linux cut last n chars

I want to cut last 17 chars

Before:
[root@localhost mysqlrecovery]# echo $a
mysql-bin.000001 mysql-bin.000002 mysql-bin.000003 mysql-bin.000004 mysql-bin.000005 mysql-bin.000006 mysql-bin.000007 mysql-bin.000008 mysql-bin.000009 mysql-bin.000010 mysql-bin.000011 mysql-bin.000012

After:
[root@localhost mysqlrecovery]# echo $a | rev | cut -c17- | rev
mysql-bin.000001 mysql-bin.000002 mysql-bin.000003 mysql-bin.000004 mysql-bin.000005 mysql-bin.000006 mysql-bin.000007 mysql-bin.000008 mysql-bin.000009 mysql-bin.000010 mysql-bin.000011