This is a Paxman 5X rim. I ordered this because I have a "5" and wanted something thinner, but what arrived was completely different from the catalog specifications, so it doesn't fit and I'm putting it up for sale. Catalog: Inner diameter 17.5mm, Rim width 3.75mm Actual measurement: Inner diameter 17.85mm, Rim width 3.5mm ※For reference, the actual measurement of the "5" is inner diameter 18.00mm, rim width 4.1mm. The 5X is quite thin. It's like new, as I only tried it once. - Brand: Paxman - Item Name: Mouthpiece Rim - Size: 5X - Engraving: 5X Will ship via Yu-Packet Post.