HES 8500 606 Fail Safe/Fail Secure, Body Only, 12/24VDC Electric Strike, Satin Brass The 8500 series is a fire rated, compact, high performance electric strike featuring a unique concealed design for use with mortise locksets without a deadbolt. Designed for fast, convenient installation, the 8500 installs with little or no modification to the frame. Simply remove the existing strike plate, remove the dust box and install. Its strength is derived from a unique keeper pin locking design, enabling the 8500 to exceed Grade-1 ratings. This unique electric strike complies with NFPA 80-07 guidelines for retrofit into fire-rated frames. The 8500 accommodates mortise latchbolts up to 3/4" throw.