Read how Lyrique Precision Barrels, LPB's, were made in the article below;

https://www.rclarinetproducts.com/how-lyrique-precision-barrels-were-made

The LPB's are made from an acoustically excellent polymer that meets and exceeds the industry standard for intonation, tone, and articulation while also being impervious to the environmental changes that plague wooden bodied instruments and barrels. This material, combined with our engineers expertise, provides for a level of consistency that simply isn't possible with wood. You'll  have no need to try six, ten, or twenty of the same model as each barrel is identical both in terms of length and bore geometry.

All LPB's have an inverse taper providing a darker more focused sound. 

The LPB's are available in 63, 64, 65, 66, 67, and 68mm's. ​