String adjusters provide fine tuning adjustment of pitch and are available in several different styles:

• Double-prong, long-lever string adjusters are probably the most common style.  Wide versions are best for use with gut or synthetic core strings.
• Suzuki-style string adjusters are specifically for use on smaller instruments sized 1/4-1/16. They are not recommended for use with gut or synthetic core strings.
• Midget style, double-prong violin string adjusters are not recommended for use with gut or synthetic core strings.
• Hill-style, single-prong violin string adjusters are primarily used for the E string, and used with loop-end strings only.