Our Free-space Electro-optic modulator (FEOM) is an electro-optical crystal-based modulator which is efficient, convenient and easy to modify the phase, polarization or amplitude of a free-space laser. We produce two versions: direct driving and resonant. Direct driving modulator requires a high voltage driver that determines the performance characters. The resonant modulator has reduced driving voltage so that it can be driven by a laboratory function generator at a fixed frequency about 20MHz. Custom versions are also available, with user-specified resonant frequencies from 0.1 to 100 MHz and a variety of AR coatings.