16 characters in the Combining Half Marks Unicode block.
U+FE20COMBINING LIGATURE LEFT HALFU+FE21COMBINING LIGATURE RIGHT HALFU+FE22COMBINING DOUBLE TILDE LEFT HALFU+FE23COMBINING DOUBLE TILDE RIGHT HALFU+FE24COMBINING MACRON LEFT HALFU+FE25COMBINING MACRON RIGHT HALFU+FE26COMBINING CONJOINING MACRONU+FE27COMBINING LIGATURE LEFT HALF BELOWU+FE28COMBINING LIGATURE RIGHT HALF BELOWU+FE29COMBINING TILDE LEFT HALF BELOWU+FE2ACOMBINING TILDE RIGHT HALF BELOWU+FE2BCOMBINING MACRON LEFT HALF BELOWU+FE2CCOMBINING MACRON RIGHT HALF BELOWU+FE2DCOMBINING CONJOINING MACRON BELOWU+FE2ECOMBINING CYRILLIC TITLO LEFT HALFU+FE2FCOMBINING CYRILLIC TITLO RIGHT HALF