Sparrows Core shims are designed to attack locks that do not have a protective collar between the core and the lock body, his is a surprisingly common feature on Lower and some mid security locks.
The attack is simple wedge the shim over the core and slide it back until it stops.
The object that is stopping it is the top pin of the first pin stack. With your pick slowly raise up that first pin until the shim finds and slide though the gap between the top and bottom pin.
The shim will now hit the second pin stack .... repeat above.... you get the idea you want to list the pin stacks and keep moving the shim back until it has covered the sheer line With the sheer line covered insert you tension wrench and open the lock.
One Pack containers 25 shims. You will not need a tension wrench until the very end to open the lock. - If the shim slide between the Core and the lock frame odds are good this will work. - If you can touch the first pin with a straight shim this bypass will work.
This is pretty easy to do and has high "that's neat" factor.