this is what I found:
REAR SIGHT HEIGHTS
GLOCK rear sights are available in four heights. The standard rear sight height for GLOCK pistols in 9x19, .40, .45 G.A.P., .357 and .380 calibers is 6.5mm (0.256in.); .45 and 10mm AUTO calibers 6.9mm (0.27in.). Rear sights are also available in heights of 6.1mm (0.24in.), 6.9mm (0.27in.) and 7.3mm (0.29in.). Every change of the rear sight height will result in a shift of the predicted position of approximately 50mm (1.97in.) over 25m (27yds.) firing distance.
reference :
GLOCK
front sights:
SOME IMPORTANT NOTES ABOUT GLOCK SIGHTS:
Factory Glocks tend to shoot anywhere from 2-4" high at 25 yards, usually necessitating the use of a 6 o'clock hold when shooting bullseye and other small targets. Keep in mind that if you lined up 20 Glocks, all of the same model and caliber, not every single one would shoot to the same point of impact with a given set of sights. Glock makes a number of different height rear sights to accommodate the inherent variations in points of impact. With this in mind, an aftermarket front/rear set with a standardized height for all models - such as the one we've been selling for a few years now - can only provide an approximate elevation setting for any particular gun.
The .215" height is the most commonly used of our front sight heights, and typically provides a point of impact from 0 to approximately 2" high at 25 yards. Results will vary with individual pistols. The .235" height front sight lowers point of impact approximately 2-3" at 25 yds from the .215" tall front sight, and the .250" height lowers the point of impact approximately 3.5-5" at 25 yds, depending on your model's sight radius. One inch of elevation change at 25 yards equates to approximately .007" of front sight height. We do not recommend sighting in your pistol at any distance closer than 25 yards, as the amount of possible error generated by sighting in at shorter distances will create issues when you shoot at longer ranges.
•Glock 17/22, 19/23, 21, and 26/27 sized guns, most common is .215" front.
•Glock 34/35, most commonly uses the .235" front.
reference :
Glock Rear Sight - 10-8 Performance Store
added on: I read one place offers a .250 front sjght not listed here