WM Dolls has recently launched a lubricant-free vagina insert that can be used on all WM Dolls. A special mucosa added to the TPE secretes lubricant when you add just a few drops of water to it (cold / lukewarm water both are ok). Tested in WM Dolls laboratories, this removable vagina can self-lubricate for about 6 months / 50 times. After that it will need lubrication in the same way as regular inserts. The lubricant-free vagina insert can be purchased in conjunction with a WM Dolls real doll (price is $50). It can't be purchased separately. Here's an introduction video of this insert: