Sigma's older 70-200mm f/2.8 for DSLR — pre-Art/Sports era with APO glass and HSM motor.
The Sigma 70-200mm f/2.8 EX APO HSM is an older generation constant-aperture telephoto zoom for DSLRs predating the Art and Sports lines. It offered f/2.8 speed at a lower price than Canon and Nikon's first-party 70-200mm lenses.
Optically decent — sharp in the centre but trailing first-party alternatives in corner performance. APO glass helps control chromatic aberration. HSM motor provides fast, quiet AF. The constant f/2.8 is useful for events and portraits.
Nikon F mount with 77mm filter thread. Approximately 1370g. No weather sealing. Full-frame coverage. No image stabilisation. Tripod collar included. EX build quality with metal barrel. Minimum focus distance 180cm.
Very cheap used. The Sigma 70-200mm f/2.8 DG OS HSM Sports is dramatically better. The Tamron SP 70-200mm f/2.8 G2 is also superior. Only worth considering at very low prices. Check for smooth focus and zoom action.