A three-dimensional model of a low-Reynolds-number swimmer is introduced and analyzed in this Brief Report. This model consists of two large and small spheres connected by two perpendicular thin rods. The geometry of this system is motivated by the microorganisms that use a single tail to swim; the large sphere represents the head of microorganism and the small sphere resembles its tail. Each rod changes its length and orientation in a nonreciprocal manner that effectively propels the system. Translational and rotational velocities of the swimmer are studied for different values of parameters. Our findings show that by changing the parameters we can adjust both the velocity and the direction of motion of the swimmer.