The Meprolight FRBS 4D pairs the company’s flip-up, rail-mountable, tritium-enhanced front (FBS) and rear (RBS) backup sights. The FBS features a self-illuminated tritium vial in its elevation-adjustable post, while the RBS’s windage-adjustable aperture is bracketed by four tritium vials (a 2D model is also available that features only two vials). Price: $195. Contact: The Mako Group; (631) 843-0490; themakogroup.com.