The ONA Block is a small, quiet workhorse when it comes to odor control. It can be put anywhere and forgotten until the odors return. The ONA Block is a small, quiet workhorse when it comes to odor control. It can be put anywhere and forgotten until the odors return. Put it in your gym bag, entrance closet or under your car seat, and it will neutralize the strongest odors, without being noticed. Ona Blocks are a fast and easy way to fight against odors at their source. Simply open and expose to the air or remove the block from the container. The duration of the block will vary but it will be effective for about 4 weeks relative to the airflow and environment around the block. To limit the amount of odor control and extend the life of the block, drill holes through the lid making it excellent for clothing storage, gym bags and diaper pails. The ONA Block is ideal for small areas such as closets, foyers, attics, cars, gym bags, boats, kitchens, garbage cans, cupboards or vents. Simply remove the cap, or punch several small holes in the cap and place in desired location. The ONA Block measures 3" x 3" and will fit in most places. The ONA Block will release its powerful odor neutralizing agent and keep the location free from undesirable odors. Replace as necessary. Available in our popular scents: Fresh Linen, Polar Crystal, and now in the incredible new ONA PRO. This amazing new formulation has been well received by our customers and they are constantly finding new uses for the ONA Block.