iTTL mode with exposure compensation RPT repeat flsh mode High speed sync. Rear curtain sync. Manual mode 15 Channels with 99IDs A, B, and C Groups with ratio control Modeling light control (on/off & intensity) AF assist beam (on and off) Control of light's audible function (on and off) 300' /100m range USB firmware upgradeable Availability of some features is camera-model dependent SPECIFICATIONS Compatible with UNPLUGGED TTL lights 2.4 GHz operating frequency 1/8,000 second maximum sync. speed Weight: 3 1/4 oz / 92 g Dimensions: 4 1/4" x 2 3/4" x 1 1/2" / 108mm x 70mm x 38mm Power source: 2 x AA batteries Weights & dimensions do not include batteries or cords. INCLUDES: 1 UNPLUGGED TTL Transmitter for Nikon 2 x AA batteries ProMaster 5398 USB firmware downloading cable for computer connection. USB micro-B.