These Hoover Style Y vacuum cleaner bags are one of the most popular bags made by hoover. The Hoover style Y bags are designed to fit any hoover vacuum currently using style Y or style Z and all WindTunnel upright models. vacuum cleaner bags. If you are not sure of the current bag style in your machine please contact evacuumstore.com to help you with your purchase. The Envirocare technology is one of the best available on the market today trapping 99.7% of allergens and particles. Some of the common part numbers associated with this item are as follows: 4010100y, 856, 856-9