That's an excellent question! Dealing with a large outdoor trash bin can be a messy chore without the right liner system. The key is finding a bag that is not only large enough but also tough enough to handle the outdoor environment.
For most large, round outdoor bins (around 32-44 gallons), I highly recommend starting with commercially available heavy-duty 33-gallon or 45-gallon trash bags. Don't use flimsy indoor bags; they will tear and create a much bigger mess. Look for keywords like "contractor bags," "outdoor," or "heavy-duty" on the package. These are typically made from thicker, low-density polyethylene (LDPE) plastic and are designed to resist punctures from sharp debris.
If your bin is a tall, rectangular "commercial" style, you'll want to look for stretchable can liners. These are often sold by dimensions rather than gallons and are designed to fit snugly, preventing the bag from falling into the bin. For areas with high rainfall or snow, prioritize bags labeled as weather-resistant or "leak-proof," which often have a thicker mil rating to prevent water from soaking through and weighing the bag down.
A good pro-tip is to ensure the bag you choose has drawn strings or tie-handles. This makes sealing and lifting a full, heavy bag much easier and cleaner. Ultimately, investing in a proper, heavy-duty liner system saves you time, prevents leaks and odors, and makes taking out the trash a far more pleasant task.