rim of the bell. Their sound is very even across dynamic levels but it can be difficult to play at louder volumes. While their bore sizes were considered large in the 19th century, German trombones have altered very little over the last 150 years and are now typically somewhat smaller than their American counterparts. Bell sizes remain very large in all sizes of German trombone and a bass trombone bell may exceed in diameter. Valve attachments in tenor and bass trombones were first seen in the mid 19th century, originally on the tenor B trombone. Before 1850, bass trombone parts were mostly played on a slightly longer F-bass trombone (a fourth lower). The first valve was simply a fourth-valve, or in German "Quart-ventil", built onto a B tenor trombone, to allow playing in low F. This valve was first built without a return spring, and was only intended to set the instrument in B or F for extended passages. Since the mid-20th century, modern instruments use a trigger to engage the valve while playing. As with other traditional German and Austrian brass instruments, rotary valves are used to the exclusion of almost all other types of valve, even in valve trombones. Other features often found on German trombones include long water keys as well as Schlangenverzierungen (snake decorations) on the slide and bell U-bows. Since around 1925, when jazz music became popular, Germany has been selling "American trombones" as well. Most trombones made and/or played in Germany today, especially by amateurs, are built in the American fashion, as those are much more widely available, and thus far cheaper. However, some higher-end manufacturers such as Thein make modern iterations of the classic German Konzertposaune, as well as American-style trombones with German features like the kranz and snake decorations. France French trombones were built in the very smallest bore sizes up to the end of the Second World War and whilst other sizes were made there, the French usually preferred the tenor trombone to any other size. French music, therefore, usually employed a section of three tenor trombones up to the mid–20th century. Tenor trombones produced in France during the 19th and early 20th centuries featured bore sizes of around , small bells of not more than in diameter, as well as a funnel-shaped mouthpiece slightly larger than that of the cornet or horn. French tenor trombones were built in both C