Signature Plastics SA family

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Signature Plastics SA family
Manufacturer Signature Plastics
Surface profile Spherical
Inscriptions Double-shot
Keycap mounts Various
BBC Micro keycaps from Comptec, for three different switch families

The SA family is a spherical keycap profile family offered by Signature Plastics. "SA" denotes spherical keycaps, with the same profile across all rows. Originally a flat profile, SA was followed by the spherical sculptured SS profile, which was later retired. SA itself was later retooled for a sculptured profile, but retained its existing name.[1]

According to Signature Plastics, this family was originally made to fit keyboards made before 1980. Currently, this family does contain space bars which measure 4, 6.25, 7 and 8 units, which were most widely used back then.

Signature Plastics SA profile.svg

Available keycap sizes and shapes

  • S: semi-matte (smooth) top and sides
  • G: gloss top and sides
  • M: matte top (rough), semi-matte sides

The size is in units × 100. Space bars are row 3 with convex top.

Rows 2 and 4 are identical. Legends for all rows can be used 180 degrees turned. 1 units row 3 keys are symmetrical by 90 degrees. For example row 4 Z can serve as row 2 Z in DE-layout. Row 3 cursor arrows are usable for all 4 directions.

Table of confirmed key sizes

Angle -13 -7 0 7 0
Size row 1 row 2 row 3 row 4 space
100C S M S M center nub (slightly off-center)
100D SGM deep dish
125 S M S M S M
150 S M S M SGM S M
175 S M S M S S M
175S S M stepped, off-center mount (like 1.25 units key)
200 S S M SGM S M Stabiliser 0.625 units left and right
200P S S M SGM S M fits on 2 switches
225 S S S Stabiliser 0.625 units left and right
250 S M S Stabiliser 0.625 units left and right
275 S S S Stabiliser 0.625 units left and right
300 SGM Stabiliser 1 unit left and right
400 S M Stabiliser 1.5 units left and right
450 S Stabiliser 1.82 units left and right
625 S fits Cherry, Filco and Leopold
700 S Stabiliser 3 units left and right, 2.25 units right
800 SGM Stabiliser 3.5 units left and right
900 S M Stabiliser 3.5 units left and right
2X2 S Stabiliser 0.625 units left and right in one row
JRET S ISO-Return (1.5x2x1.25)


  1. Pimp My Keyboard — The Origin of SP Keycap Families

See also