Bulldogs 900kg round jacks are recognized as the industry standard by leading agricultural, commercial, horse, livestock, and other trailer manufacturers. For more than three quarters of a century, BULLDOG jacks have been demonstrated to be the most reliable, field-proven jacks on the market. Smooth, comfortable, ergonomic design. Dependable vertical and side load capacity. Proven reliability for long term use at rated loads. Precision fitted parts for extra stability. A-Frame models listed have grey painted outer and inner tubes - All other models have grey painted outer and clear zinc inner tubes.