Thank you for viewing! I've customized the rubber grip section of a Jetstream 4&1 multi-pen with a carbon fiber replacement. This is a straight barrel. This listing is for the metal grip section and wood parts only; the pen body itself is not included. There is no warranty. If it breaks, please reattach the original rubber grip. I will wrap it in bubble wrap and ship it via Nekopos (a Japanese postal service). Shipping will be on weekends due to my schedule, so please allow some time. For those who understand handmade items, how about it, including shipping? Carbon fiber is a lightweight and durable fiber made by carbonizing acrylic fibers, petroleum, or coal at high temperatures. Although it is a thin thread on its own, it is combined with resin to create composite materials such as "carbon fiber reinforced plastic (CFRP)" and is used in a wide range of fields such as aircraft, automobiles, and sporting goods. Its main features are lightness, strength, and high heat resistance and corrosion resistance. Thank you for viewing! As a stationery enthusiast, I love using Jetstream and Dr. Grip 4&1 pens. I dislike the deterioration of the rubber, so I started making them for myself using scrap wood from famous trees that I had collected. You can customize these practical pens to your liking, just like changing your smartphone case. I hope that my handmade wooden pen and wood parts can be of some help in your daily work, study, tests, qualifications, and entrance exams. For those who like handmade wooden pens, those who like the works of wooden pen workshops such as Craft A, Nohara Kougei, Koubou Kusabi, Kobuta Koubou, and those who like multi-function pens such as Jetstream 4&1, Dr. Grip 4&1, and Pure Malt Premium 2&1, how about it? I create them using famous woods such as Karin Burl, Karin Red and White, Snakewood, Pink Ivory, Desert Ironwood, Black Persimmon, Black Persimmon Peacock Grain, Red Sandalwood, Ebony, Rosewood, Sandalwood, Palo Santo, Briar, Rosewood, and Satine. #jnsm