This is also why the inner "waist" dimension is so vital to those harmonic frequencies. Clarinet bodies have been crafted from numerous components adding wood, plastic, hard rubber, metal, resin, and ivory. The overwhelming majority of clarinets utilized by professionals are crafted from African hardwood, mpingo African Blackwood or grenadilla, rarely as a result of diminishing provides Honduran rosewood and sometimes even cocobolo. Historically other woods, notably boxwood, were used. Most low-cost clarinets are made of plastic resin, reminiscent of ABS. Resonite is Selmer's trademark name for its kind of plastic. Metal soprano clarinets were time-honored in the early 20th century until plastic devices supplanted them; metal construction continues to be used for the bodies of a few contra alto and contrabass clarinets and the necks and bells of nearly all alto and larger clarinets. Ivory was used for a few 18th century clarinets, but it tends to crack and doesn't keep its shape well. Buffet Crampon's Greenline clarinets are made from a composite of grenadilla wood powder and carbon fiber. Such clarinets are less littered with humidity and temperature changes than wooden contraptions but are heavier. Hard rubber, similar to ebonite, has been used for clarinets because the 1860s, although few modern clarinets are made from it.