The 717AH is back and with a slight price drop. [Thanks Larry]. This is a solid and inexpensive mount for the top of your sliders or track dollies that help to reduce vibration during your movements. It's also helpful to be able to change pan and tilt angles. You'll find this head on many DIY projects including Rod's DIY Ladder dolly. You can find the discounted 717AH following the link (click here).
Fluid Drag Tripod Head 717AH