The Filter Cartridge for STIL Top Load Twin Pak – Coreless is a premium filtration set designed specifically for Bullfrog STIL spas (2018–present). Each pack includes two 10-00281 filters that provide efficient water cleaning and long-lasting performance. These coreless filters are also compatible with STIL spas from 2015–2017 when used with the Filter Cage Core Assembly (#10-00417). Ideal for maintaining crystal-clear water and optimal circulation in your spa system.