The LVL series includes five different size options, from 42mm up to 75mm in diameter, so you can get a levelling adapter that'll fit the diameter of your particular tripod head.

1/2-ball levelling bases tend to only come with complete tripods, such as Vanguard's Alta Pro 3VL, but now Vanguard has launched a new line of separate levelling adapters: the LVL series.