Spaarti cloning cylinders were four-meter-tall tanks that acted as mechanical wombs filled with nutrient chemicals and organic catalyzers, used for the creation of personal clone armies by those wealthy and/or well-connected enough to acquire them.
To create clones from Spaarti cylinders was the fastest known form of cloning. Kaminoan cloning had a single clone grown safely at maturity in ten years. With a Spaarti cloning cylinder, a fully-mature adult Human could be grown in a staggeringly quick one standard year. However, Kaminoan cloning was much more effective, for ten years of growing in constant learning and training resulted in creating perfect warriors despite the long wait. Spaarti clones did not receive any training, instead they had their personalities formed by a process known as "flash-pumping," which involved writing the memories of another person to a fresh clone's brain. Spaarti clones grown in less than a full year had the dangerous side effect of possible clone madness. However, Thrawn discovered that using ysalamiri to cut off the clone's connection to the Force would enable the creation of the clone within 15 to 21 standard days.
They were built by Spaarti Creations, on the planet Cartao. They seem to have their origins in both Khommite cloning technology, which had for a millennium been developed to a level far surpassing that of the rest of the galaxy, and Kaminoan technology.
Cloning cylinders were thought to have been destroyed during the Battle of Cartao, but a few thousand units survived. The Galactic Republic used Arkanian Microtechnologies' Spaarti clones to complement the Kaminoan clone army.
At the near end of the Clone Wars, all but a few were unaware that Supreme Chancellor Palpatine had secretly commissioned a second clone army, which differed from the Kamino-bred Fett clones in two primary ways: they were grown to maturity in roughly one year as opposed to ten years, and they were created on Centax-2 instead of Kamino. Omega Squad noticed this, adding to their suspicions about Chancellor Palpatine's intentions. The clone troopers of the 14th Infantry Brigade were among the first generation of Spaarti-grown Fett clones and vanguard of what was to come in Palpatine's New Order, while others were assimilated into the 501st Legion and the Coruscant Guard's shock troopers.
While the Spaarti Fett clones numbered in the billions, and were thus possibly far more numerous than the depleted numbers of their Kaminoan-bred Fett brethren, the Spaarti clones were given only flash-training on the basics of being a soldier, such as how to fire a rifle. When first sent into action, the clones of the 14th did not bother to take cover from enemy fire, and their weapons accuracy was surprisingly pitiful, as noted by the commandos of Omega Squad. Also, they were completely unaware of all things Mandalorian, thus indicating that the Mandalore culture was never introduced to the Spaarti clones.
Ultimately, the clones of the 14th Infantry were a sign of a new breed of clones to come: the clone stormtrooper. While the amount of clone stormtroopers, from all genetic sources and not just the Fett template, was far greater than the GAR, clone soldiers bred for the Galactic Empire generally exhibited poor marksmanship and lacked in battlefield tactics. Their strategy basically involved charging towards the enemy, weapons blasting, until all targets were neutralized - regardless of clone casualties. They were even known to refuse to follow orders and fire on their own allies because of the clone madness. As a result, the Empire eventually abandoned the technology and pursued the process of recruiting troopers in more traditional ways.
Joruus C'baoth observes Luuke Skywalker's creation on Mount Tantiss.
Emperor Palpatine also kept several private stores of these devices, which he used both to clone the insane Dark Jedi Joruus C'baoth from recovered samples of the original's DNA and to clone new vessels for his dark essence.
In 9 ABY, Grand Admiral Thrawn discovered approximately 20,000 cylinders in the Emperor's secret storehouse in Mount Tantiss on Wayland and used them to create an army of clones to man his Dreadnaught fleet. Later, Thrawn sent one of the cloning cylinders to the Hand of Thrawn fortress on Nirauan, and began growing a clone of himself.
Grappa the Hutt also used Spaarti cylinders as part of his plan with Black Sun to replace members of the Imperial Interim Ruling Council with clones.