The purpose of the study was to investigate the effectiveness of the manipulatives in instruction of mathematics to those who have learning disabilities. Two middle school students who revealed very low achievements in the previous mathematics tests were involved in this study. Unit Cubes were used as the manipulatives, and the researchers utilized this manipulatives to teach the number bases. After a series of instructions utilizing the Unit Cubes, the subjects were interviewed with semi-structured form. In general, the effect of using the manipulatives were positive. Both subjects could understand much better with the Unit Cubes, and revealed affirmative results such as their positive attitudes toward mathematics.