Luis Rossi began experimenting with clarinet design and building in the late 1980's. Rossi instruments feature hand-carved thumb rests, split register vent/throat Bb key, and all the other standard features of Rossi clarinets. At that time he was using a sleeve insert in the barrel, which fits into an indentation in the top of the body to eliminate the gap caused by pulling out the barrel for tuning. Also, both models currently being manufactured (Honduran one-piece, and Bb Cocobolo) have alternate Ab/Eb keys for the left hand little finger (side lever). Both models are large bore (English model) instruments. Rossi now offers three different bore configurations (English, French, and American) in at least four woods (east African blackwood, cocobolo, and 2 other varieties of dalbergia). Between 1990 and 1994 changes include: no more sleeve in barrel, addition of "ivory" rings, all tone holes are now inserted with hard rubber to improve sealing, and slight changes in the appearance and positioning of the key mechanism.