Uni Kuru Toga

Some Kuru Toga mechanical pencils. Top to bottom: an Alpha Gel, a Standard, and a Roulette model

Animation showing the revolving mechanism of the Kuru Toga mechanical pencils

Kuru Toga is a mechanical pencil line developed by the Uni Mitsubishi company. The special feature of this pencil is a particular mechanism (referred as "Kuru Toga Engine") which rotates the lead every time the tip is pressed and then released from the paper surface. This mechanism prevents the tip from becoming chisel-shaped (therefore more prone to crumble or break) and ensures a consistent line width. The tip rotation is obtained by a spring and three gears, and the revolving action is visible by a rotating logo.
All models except the "Pipe Slide" and the "Advance", rotate the lead approximately 9 degrees per stroke (40 strokes for a complete revolution).
"Pipe Slide" and "Advance" versions rotate the lead twice as fast per stroke: approximately 18 degrees per stroke (20 strokes for a complete revolution), thus they are more suitable for Western characters which are made of fewer and longer strokes compared to Asian characters, and also for use with softer leads (such as 2B) which wear down more quickly. "Pipe Slide" and "Advance" versions also share a sliding sleeve.
All Kuru Toga pencils are available in 0.5 mm and in a variety of colours, but some models are also available in 0.3 mm and 0.7 mm. There are also special limited editions featuring characters by Disney, Peanuts, Sanrio and Studio Ghibli.
"Roulette" and "High Grade" use the Uni eraser refill size C, while all the other models use the Uni eraser refill size S.

Kuru Toga pencil models

Model name	Available Sizes	Spare Uni Erasers	Additional Features / Informations
Standard	0.3mm 0.5mm 0.7mm	Size S	Plastic body; plastic clip; available in a wide variety of colours
High Grade	0.3mm 0.5mm	Size C	Ridged aluminium grip section; metal clip
Roulette	0.5mm	Size C	Knurled aluminium grip section; metal clip
Rubber Grip	0.5mm	Size S	Rubber grip area; no clip (replaced by a little knob)
Alpha Gel	0.5mm	Size S	Same gel grip as the classic Alpha Gel; plastic clip
Pipe Slide	0.5mm	Size S	Plastic body; plastic clip; sliding sleeve; faster rotation
Advance	0.3mm 0.5mm 0.7mm	Size S	Plastic body; metal clip; sliding sleeve; faster rotation

Special Editions

Edition	Model Type	Available Sizes
Disney	Standard Rubber Grip	0.3mm - 0.5mm 0.5mm
Peanuts	Standard Rubber Grip	0.3mm - 0.5mm 0.5mm
Sanrio	Standard	0.5mm
Adidas	Standard	0.5mm
Studio Ghibli	Advance	0.3mm - 0.5mm

The Muji version

Muji mechanical pencil featuring a rotating lead mechanism

Japanese company Muji produced a mechanical pencil with the same rotating lead mechanism as the original Kuru Toga. It could be found in the Muji online catalog until 2018.
The pencil (only available in 0.5 mm) has a white plastic body and a plastic clip, and is manufactured in China.
According to the Muji website, this model was marketed under the generic name "Mechanical Pencil 0.5 - White" and described as follows: "When writing the lead is rotated while being used to maintain a certain lead thickness".