Opteka 25mm Auto Focus DG EX Macro Extension Tube for Nikon D4s, D4, D3x, Df, D810, D800, D750, D610, D600, D7200, D7100, D7000, D5500, D5300, D5200, D5100 and D3100 Digital SLR Cameras Extension tubes are designed to enable a lens to focus closer than its normal set minimum focusing distance. Designed with all the circuitry and mechanical coupling to maintain auto focus and TTL auto exposure with Nikon SLRs Durable aluminum mount Glass-free; Lightweight 1 Year Opteka Warranty