and High Quality Color: Blue Qty: 4 pcs These are Z-type foam filters compatible with various models of inflatable hot tubs. Please note that similar filters may come in non-round shapes such as square or hexagonal. These alternative shapes are often the result of lower manufacturing standards and may not fit as effectively as round filters, which provide a more consistent surface area for filtration. Some of these filters are also excessively thick, which can restrict water flow and place added strain on the pump. After using original equipment filters for approximately 12 months, it was observed that they lasted about one week and were difficult to clean. This led to the development of an improved foam filter alternative. After extensive testing, the filters offered in this listing were selected for their performance and durability. They have been in continuous use with no issues. These filters are more cost-effective than original filters, allow better water flow, and provide improved filtration. Round filters have been sourced to ensure a proper fit and optimal performance compared to irregularly shaped alternatives. Due to their design, they offer consistent filtration efficiency. For best results, it is recommended to use bromine as a sanitizer, as it is odorless, gentle on skin, and compatible with foam filtration systems. If chlorine is used, regular filter replacement is advised to maintain system performance. It is normal for these filters to experience slight color fading with use. This does not affect functionality. Unlike some sellers who dye foam green to mask discoloration, transparency in product appearance is prioritized.