Newtonian telescopes are sensitive to the precise alignment of the primary and secondary mirrors. Otherwise, their performance will suffer, making nighttime observing difficult or even impossible.
Fortunately, the secondary mirror can be precisely adjusted, but this requires some kind of tool, such as a screwdriver or Allen key. This procedure carries a certain risk: if the tool slips from your hand and falls onto the primary mirror of the Newtonian telescope, it may damage it. Not to mention that these tools are often unavailable precisely when they are needed most! Installing collimation screws solves both problems at once, allowing the secondary mirror to be adjusted by hand.
The collimation screws recommended for Newtonian telescopes are compatible with most 13 cm or larger Celestron / Orion / SkyWatcher Newtonian telescopes, including Dobsonian models. The shorter version is 35 mm long, while the longer version is 45 mm.