G Pen Engineers The Most Advanced, User-Friendly Portable Vaporizers. Leading at the forefront of ingenuity and aptitude, G Pen was the first to market a tank system specifically designed for essential fluids and personal aromatherapy regimens. Grenco integrates superior functionality with the convenience of transportability. Their mission is to create high-powered vapes with innovative technology at a price point everyone can access. Grencohas become a byword for ‘quality’ when it comes to portable vaporizers.