IETLAB GenRad 1422 Series Variable Air Capacitors (0.002 pF - 1150 pF)

(Full specifications can be found on datasheet)

Range as low as 0.002 pF and as high as 1150 pF (Depending on Model)
Stability: better than 0.02% full scale per year
Settable to 40 ppm
Low temperature coefficient, low losses
Wide selection to suit needs

Datasheet