Philip,
If you're interested in what a "standard" servo really is, and what the various other types of servos are, look them up at
http://www.hitecrcd.com.
Servos come in various classes: Giant, Standard, Mini, Micro, Sub-Micro. While the HS-55 may be
your standard servo, it is in reality a
sub-micro servo. In fact, none of the servos recommended so far in this thread are
standard servos. The HS-81 is a
micro servo. The HS-225 is a
mini servo. Standard Hitec servos measure about
: 1.6"x0.8"x 1.4". Standard servos from other manufacturers are approximately the same size.