Exercise bands

Hootsmon

The long and wide and heavy duty squat band types.....these really work nearly as well as free weights if used properly?

VimFuego

resistance is resistance, though the resistance curve is slightly different with bands than weights (it's at peak contraction whereas with weights it's at the beginning of the contraction). The main issue with bands is maintaining intensity for progressive overload, it's hard to keep adding bands, much easier to add 5 kilos to a barbell.
Personally I prefer bands as they are more flexible and I'm not a full on power lifter or body builder, so for my fitness goals they work well. 

Hootsmon

Ta Vim