Abstract: A hand-held implement, is provided with a body including an elongated snap-fit post and an elongated snap-fit cartridge housing. The snap-fit cartridge housing includes a coaxial recessed groove and readily snap-fits into the body of the pen by the resilient engagement of the tip of the snap-fit post into the coaxial recessed groove of the snap-fit cartridge housing. The cartridge housing can be readily removed from the body of the pen and replaced with another cartridge housing inserted in its place. The body of the implement has external surfaces which define contours which match and ergonomically engage the surfaces of a user's thumb and fingers when the user grasps the implement, so as to provide a large surface area of contact between the user's hand and the implement.

Abstract: A hand-held implement which is sufficiently small so that it does not extend beyond the hand of the user and has forward and side surfaces which are oriented so that the implement in use extends in a direction which is no further toward the thumb of the user than the index finger of the user. The forward and side surfaces can be provided with concave contours which engage the thumb and fingers of the user.