The utility model relates to an oil well logging technical field, concretely relates to four multi -functional arm hole diameters, including last joint Assembly, motion mechanism component, power drive assembly, shell body part and electronic component. Go up joint Assembly and be connected with motion mechanism component, go up joint Assembly and be connected with the shell body part, the motion mechanism component be connected with power drive assembly, the motion mechanism component install inside the shell body part with power drive assembly, power drive assembly and shell body part are connected with electronic component respectively. This instrument adopts motor drive and spring combined mechanism, is an instrument with centralizer, eccentric, caliper equi -join, the use quantity of logging instrument and instrument when having significantly reduced the well logging. This four multi -functional arm hole diameters can help the telescoping ram to realize effectively pushing away leaning on in irregular well section when using with the telescoping ram combination for the log data is more accurate reliable.