Inky Paw Silicone Grease
100% silicone grease for eyedropper conversions (e.g. Preppy or Kaweco), or to lubricate your piston mechanism fountain pens (e.g. TWSBI and Pelikan).
This little jar contains 1/8 oz. of silicone grease, which will go a long way for your pens. The silicone grease is clear, waterproof and safe to use with plastic pen parts.