CFKIT Maintenance Filter Kit for Kubota ZD321 HST Zero Turn Mower w/ Kubota Eng. Kubota ZD321 Zero Turn Mower w/ Kubota Eng. If you desire a specific brand, please inform us prior to placing your order. With CFKIT, you will receive High Quality Filters from the most known brands. Can’t find your kit? If you have questions about the product or your order please. EST, MON – FRI.