Parts of a Pin Curl – Base, Stem and Circle Diagram

All 12 parts on the diagram

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The three parts 3

Base The part that stays still, attached to the scalp. The curl is built on it.
Stem The strand between the base and the circle. It gives the curl its direction and movement.
Circle The part that forms the curl itself. Its size sets the width of the wave.

Stems 3

No-stem The circle sits right on its base. It is the tightest curl, with the least movement.
Half-stem Half of the circle sits on its base, half off. It moves a little more.
Full-stem The circle sits completely off its base. It is the loosest curl, with the most movement.

Bases and centers 6

Rectangular base A four-sided base, longer one way. It is used mostly at the front and sides.
Triangular base A three-sided base, used along the front hairline.
Square base A base with four equal sides.
Arc base A base shaped like a C or a half-moon.
Open center A circle with a hole left in its middle. It gives an even, smooth wave.
Closed center A circle wound tight to the middle. It gives a tighter curl.

How this list was compiled: Every name checked on 2026-10-01 in two sources. (1) Oklahoma Department of Vocational and Technical Education, Curriculum and Instructional Materials Center, Basic Operator, Teacher Edition, Cosmetology Series (1993), unit Pin Curling, an openly published state curriculum (ERIC ED 380 613), https://archive.org/details/micro_IA41153613_0633 (a pin curl's three main parts: base, the area attached to the scalp; stem, which joins the scalp area to the curl and determines its mobility; circle, which forms the actual curl. Three stems: the no-stem curl sits right on its base and is the tightest, with the least mobility; half of the half-stem curl sits on the base, half off; the full-stem curl sits off the base and has the most mobility. Bases: arc or C shaping, also known as half moon; rectangle, usually used on sides and front; square; triangle, usually used around the front hairline. Open centers give even and smooth curls and a looser wave; closed centers are tight). (2) Standard Textbook of Cosmetology, 1967 edition, read through the Internet Archive's full-text search, https://archive.org/details/standardtextbook0000warr (pin curls are constructed of three principal parts: base, stem and circle; the base is the stationary or immovable foundation of the curl, attached to the scalp; the stem is the part between the base and the first arc of the circle, which gives the curl its direction, action and mobility; the circle is the part forming a complete circle and governs the width and strength of the wave; no-stem, half-stem and full-stem; rectangular base, triangular base, square base and arc base, also known as half-moon or C shape; an open center gives an even, smooth wave and a closed center is the other kind). Licence: own work

The drawing: Drawn for this site on 2026-10-01 from plain geometry. Own original drawing; nothing traced or copied. Licence: own work

How it works

The three parts of a pin curl are the base, the stem and the circle. Tap a number to read what each part does, then take the quiz. Two more views show the three stems and the base shapes.

Read the full guide

Base, stem, circle

The base is the patch of scalp the hair grows from, and it does not move. The stem is the strand from the base to the circle's first turn; it gives the curl its direction and movement. The circle is the coil at the end, and its size sets the width of the wave.

Stems and bases

A curl is named for where its circle lies: on the base (no-stem), half off it (half-stem) or wholly off it (full-stem). The longer the stem, the looser the curl and the more it moves. The base is named for its outline: rectangular, triangular, square or arc.

Questions and answers

What are the three parts of a pin curl?

The base, the stem and the circle. The base is the stationary part attached to the scalp. The stem runs from the base to the first turn of the circle and gives the curl its direction. The circle forms the curl itself.

What is the difference between no-stem, half-stem and full-stem curls?

It is where the circle sits. On a no-stem curl the circle lies right on its base, and the curl is the tightest. On a half-stem curl it lies half off the base. On a full-stem curl it lies off the base and moves most.

What are the pin curl base shapes?

Rectangular, triangular, square and arc. An arc base is also called a half-moon or C-shape base. The shape is the outline of the section of hair the curl is made from.

What is an open-center pin curl?

A curl whose circle leaves a hole in the middle. It gives an even, smooth wave. A closed-center curl is wound tight to the middle and gives a tighter curl.