Planner refills are inserts or pages designed to be added to a planner binder or cover, allowing users to update or customize their planning system without purchasing a new planner. They are typically used in ring-bound or disc-bound planners, where pages can be easily removed and replaced. 
Planner refills come in various formats, including daily, weekly, monthly, and yearly layouts, as well as specialized pages like to-do lists, habit trackers, budget planners, and notes. They are available in different sizes to fit various planner systems, such as A5, personal, or pocket sizes.
To use planner refills, you first need a compatible planner binder or cover. Once you have the binder, you can select the type of refill that suits your planning needs. For instance, if you prefer a weekly overview, you would choose a weekly layout refill. 
To insert the refills, open the rings or discs of your planner, remove any outdated pages, and add the new refills. Ensure the holes in the refill pages align with the rings or discs of your planner. Once inserted, close the rings or discs to secure the pages in place.
Planner refills offer flexibility and customization, allowing users to tailor their planners to their specific needs and preferences. They are also cost-effective, as you only need to replace the pages rather than the entire planner. Additionally, they are environmentally friendly, as they reduce waste by reusing the planner cover or binder.