Answer:
We are five little objects of an everyday sort, You will find us all in a tennis court.
A box without hinges, lock or key, yet golden treasure lies within.
Slayer of regrets, old and new, sought by many, found by few.
What can go through glass without breaking it?
There are millions of me. I am very small but when moving fast I am deadly.
Iām grown from darkness but shine with a pale light. Very round I am and always a lady's delight.