Block from U+02B0 to U+02FF. This block was introduced in Unicode version 1.1 (1993). It contains 80 codepoints.
The Wikipedia provides the following information on block Spacing Modifier Letters:
Spacing Modifier letters is a Unicode block containing characters for the IPA, UPA, and other phonetic transcriptions. Included are the IPA tone marks, and modifiers for aspiration and palatalization.