AVOID materials like jelly and rubber and other porous materials. Personally, I won't consider anything below an 8 on Eden's safety scale. This is especially important if you are looking for toys to be used by two people. Jelly and rubber are porous and common allergens and may off gas chemicals which aren't body safe. They cannot be sanitized and will retain bacteria and other microbes and moisture which will allow the bacteria to flourish even further. This is a safety risk even between fluid bonded partners, or even for using a toy solo by a single user. 2-3 out of a possible 10 is not safe at all. These materials also don't last nearly as long, eventually break down, will be more sensitive to chemicals, heat and other factors, may react to other toys, are harder to store and much harder to clean. Look for silicone toys. Your options for double dildos will be slimmer but much, much safer and longer lasting. Glass is also an option though you may not want the firm material depending on what you're planned use for it is. Both silicone and glass are body safe, non-porous, hypoallergenic, completely sanitizeable. If you are dead set on the jelly or rubber, I would highly recommend putting a condom over it during use to prevent it from absorbing fluids and prevent contact of the material with your body, especially mucus membranes.