Tips / Systems

15 System 15 System · short Plus

A short path that hits the near short rail first and comes back across the two long rails. Subtract 15 and the departure number from the arrival number to find the first aim point.

Formula / route reference

First cushion A = arrival D − 15 − departure S

When to use it

Short short-long-long layouts where both the departure number and the third-cushion arrival number are 40 or less. Check this narrower range first compared with the regular Plus.

Written and edited by TTBoys · How we write and check sources · Report an error

Sources and diagrams reviewed: 2026-10-04. Rules of thumb are practice references for a specific diamond scale and stroke. Geometric constructions are kept separate from real trajectories, and nothing was measured on a real table. On mobile, the table stays in landscape so the directions in the text match the diagrams.

Compare in the simulator

Presets are comparison examples from a physics model; they do not guarantee the formula's real-world accuracy or a point.

What do you read from the layout?

Start 10: the starting diamond on the long rail.
Target 35: halfway between 30 and 40.
First cushion 10: from 35 − 15 − 10.

Slope and correction: 15 is a fixed term, not an angle value. Read the start line again, but first check that both the start and the arrival are within 40.

See the worked example and layout See related practice

What to know first

The white ball is the cue ball you strike. The long sides are the long rails and the short sides are the short rails. The numbers are names given to the diamond marks for calculation, not centimeters or angles. Dashed lines are reference lines you read by extending them backward; arrows show the order in which the ball travels. This article uses INPROD's 15 System table.

1. Read the departure and arrival numbers

10, 20, 30, 40 along the long rail from the corner nearest the first short rail. Red departure and white arrival use the same number at the same position. Yellow first cushion goes up by 10 per diamond from the corner marked 0.

Red S · departure number: read it by extending the aiming line back behind the cue ball.
Yellow A · first-cushion aim number: the spot you calculate and aim at.
White D · arrival number: the target on the cushion you want to send the ball to.

First choose the third-cushion arrival point D you want on the white scale. In the example it is 35, halfway between 30 and 40.
Extend the line the cue ball will travel backward to read the red departure number S. It isn't always the number right next to a ball sitting inside the table.
If the departure or arrival goes over 40, you are outside the range of this beginner table. Consider the regular Plus or Maximum Plus.

2. Aim at 35 − 15 − 10 = 10

35 − 15 − 10 = 10

Arrival 35 minus 15 is 20. Subtract departure 10 and the first cushion is 10. First cushion 10 is one diamond from the top corner.

35−15−10=10: first short rail at 10 → long ② → long ③ at 35 → the two object balls. Keep the arrival 35 and the position of object ball 2 apart.

Red dashed line: extend the first aim line backward to read the start number
White line: the order in which the cue ball travels around three cushions
Yellow line: an example of meeting the two object balls after the third cushion

A sketch of the worked example's ball layout and travel order. Where the ball actually lands depends on thickness, spin and speed.

3. Short → long → long: follow all three

① short rail at yellow 10 → ② the adjoining long rail → ③ long rail at white 35. This much is finding the 3-cushion path. A scoring layout that hits both object balls has to be checked separately.

The source's reference is 3 tips of side spin. In this diagram's direction practice with left running English; in the mirror-image layout, right running English. Get the reference shot right first without changing the tip height or tip units.
Power isn't about hitting hard; set a consistent stroke that reaches the third cushion. Check first cushion 10 first, then the area around arrival 35.
If the cue ball sets off after hitting a ball first, read S again from the cue ball's line after the collision. Don't plug in the original cue ball position.
Practice problem: with departure 15 and arrival 35, the first cushion is 5. Aim halfway between corner 0 and the first diamond, 10. If the calculation comes out negative, don't force it onto this example's direction.

The diagrams are concept drawings that explain the numbers and the cushion order. They do not guarantee an exact path or a successful score given ball size, spin, speed and table condition. Repeat a reference shot on a real table with the same tip position and power, and adjust.

Practice with the example layout

Back to the worked example and layout ↑

Follow the yellow first cushion 10 → the second cushion, a long rail → arrival 35, then the ball comes out toward the object ball. 35 is the third-cushion target, not the position of the last ball.

Point to the cue ball, the ball you hit first and the last ball, and say the cushion order.
Repeat the same layout 5 times and record where the first cushion and the calculated target actually land.
If the first cushion is already off, check your aim and thickness; if the first cushion is right but later ones drift, check spin and speed. Change only one thing for the next 5.

Sources and verification

INPROD · 국제식대대 3쿠션 당구 15시스템 — Checked the original number table, the 35−15=10+10 example, the 40-or-less departure/arrival range and the 3-tip condition.

Sources may use different diamond scales and conditions. The text notes which scale it uses and the limits of what was checked; the diagrams are our own concept drawings.