The phrase "a length of only" is correct and usable in written English.
It can be used to specify a measurement that is minimal or less than expected.
Example: "The cable has a length of only two meters, which is insufficient for our needs."
Alternatives: "a mere length of" or "just a length of".
The device has a length of only 29 µm and operates at 40 Gbit s−1.
Velociraptor was smaller than Deinonychus, reaching a length of only 1.8 metres (6 feet) and perhaps weighing no more than 45 kg (100 pounds).
A neutron spin polarisation device with a length of only 160 mm and a cross-section of 22×34mm2 is presented.
Usually, it is between 1 and 2 centimetres in length, but it may have a length of only 2 millimetres before dividing.
Thus, the remaining trimmed candidate route has a length of only 64 meters.
By the 25th tail vertebrae, the filaments on the underside reach a length of only 35 mm.
His loss overwhelms us.. Macdonald served just under 19 years as Prime Minister, a length of service only surpassed by William Lyon Mackenzie King.
The top pipe of a 2-foot stop has a speaking length of only three-quarters of an inch, and this is about the practical upper limit.
It is also not uncommon for grindcore albums to be very short when compared to other genres, usually consisting of a large tracklist but having a total length of only 15 to 20 minutes.
Even for a diffusion length of only 0.5 μm in a 3-μm-thick absorber, and no contribution from the CdS layer, an optimum back bandgap of 1.35 eV is found, yielding short-circuit current densities of 36.0 (33.5) mA cm−2 for a front bandgap of 1.05 (1.68) eV.
Among that clade, Nigersaurus was fairly small, with a body length of only 9 m and a femur reaching only 1 m.
