SEOs work by filling the muscle up with an oil substance. It is site-injected directly into the muscle whose size is to be increased. SEO is usually used to ‘top up’ a muscle that is not quite up to standard with the rest of the body. SEOs help promote muscle growth by stretching the fascia of a muscle; this allows the muscle to gain size quicker since the primary restrictive factor of muscle gain is the fascia.[citation needed]

A site enhancement oil is not an androgen and contains no steroids.
http://en.wikipedia.org/wiki/Site_enhancement_oil