A balance weight for a wheel of a two-wheel vehicle includes a weight body made from metal other than lead and a clip made from spring steel. The lockable safety selector switch has a body adapted to selectively orient between a SAFE position that prevents the firearm from firing and a FIRE position that allows the firearm to fire, and a locking mechanism configured to operatively associate with the firearm selector detent pin to selectively lock the body in the SAFE position. The systems include one or more spacers and a mechanical actuation means for delivering and deploying the spacer.