Apparently, this pickup is called a Combine Ring, which has only been in one other Sonic game (Knuckles Chaotix).

The powerup causes your rings to group themselves into larger rings when you drop them, making them easier to pick up.

In Sonic Mania, the effect of the Combine Ring is slightly different compared to the effect in Knuckles' Chaotix. Instead of an icon appearing at the bottom, when a character is holding a Combine Ring the Ring counter will turn blue and the Combine Ring icon will appear next to the total. Also, instead of one large Ring being dropped upon taking damage, a few large Rings are dropped, each returning a small portion of the original Ring count when re-obtained.

I must have gotten more of these than I thought, because I assumed the giant rings were just a new feature since it seemed to happen a lot of the times I dropped my rings in large quantities...

According to Eurogamer, collecting every ring in a bonus stage earns you a 'Perfect', which is required for getting a Gold Metal.

The trick to getting a Perfect is to collect every ring on a stage. You may notice you can finish a stage without collecting all the rings, despite seemingly collecting all you can see; that's because you can convert spheres into rings by creating an outline around groups of blue spheres. These can be squares or rectangles, groups that already have partial outlines already completed, or have unusual shapes, such as bouncing spheres cutting into the corners.

The trick, then, is to make sure you have converted all groups of blue spheres into rings before you collect any remaining individual blue spheres. The easiest way to do this is to leave behind one or two blue spheres that cannot be converted, getting the 'Perfect', then going back to those spheres you left.

It's worth noting that, as mentioned in our Sonic Mania unlockables page, getting all gold medals doesn't unlock anything in game - only Silvers is required. It's only if you want all Trophies or Achievements that Gold is worth aiming for.

_{Screenshot from Giantbomb's 'Quick Look: Sonic Mania'}

Sources

• Eurogamer: Sonic Mania special stages - How to get Chaos Emeralds and Gold Medals from UFO, Blue Sphere stages
• Giant Bomb: Quick Look - Sonic Mania