When sourcing hydraulic bottle jacks, the most critical factor is the Rated Capacity, which must exceed the maximum load by at least 20% for safety margins. Buyers should prioritize jacks with a solid forged steel base rather than cast iron to prevent leaking under high pressure. Additionally, verify the Minimum and Maximum Height (Stroke) to ensure compatibility with the intended lifting points, and look for a safety bypass valve that prevents the piston from over-extending or the jack from being used beyond its rated capacity.