Venus replacement heads are available with 2, 3, and 5 blades.
Most Venus refill heads fit standard Venus refillable handles. There are exceptions: Simply Venus refills and the Venus for Pubic Hair and Skin line have specific compatibility rules. In particular, pubic-area refills only fit Venus for Pubic Hair and Skin handles.
Venus refills are sold in several pack sizes, commonly in 1-, 4-, 5-, 6-, and 8-cartridge packages.
Many Venus refill cartridges are described as lasting up to 30 days when shaving about twice per week. Actual lifespan can vary depending on how often and how you shave.