De or het heldring?

The correct Dutch article is:

de heldring

Rule Words ending in -ing: almost always de. See the rule

How to use heldring

the heldringde heldring
this heldringdeze heldring
that heldringdie heldring
our heldringonze heldring
your heldringjouw heldring
every heldringelke heldring
which heldring?welke heldring?
a big heldring / the big heldringeen grote heldring, de grote heldring