"No damage from your own Bombs"
The Bombproof Ring is a Magical Ring that Link can obtain in Oracle of Seasons and Oracle of Ages. Link can acquire the ring by planting a Gasha Seed and finding it within a Gasha Nut. He can also acquire it in a Seed Ring form by bumping into Maple. The ring can also be obtained through a Fortune Link at Vasu's jewelry store.
When equipped, the Bombproof Ring makes Link immune to damage from his own Bombs. While it might not appear to be a very useful Magical Ring, it could be used during certain Boss or Mini-Boss battles where Bombs are used. Link can toss bombs a bit more carelessly, as he does not need to worry about taking damage himself.