Makes collimation easy, so simple and well made, if you've got a reflector telescope get one.

My first scope, an old Helios 200 Newtonian, came with a laser collimator. After hours of tinkering and frustration I bought this from Flo and whilst waiting for it to arrive read a guide from Skywatcher as to how to use a collimation cap. Following that guide, not the slightly baffling included instructions, I had the scope perfectly collimated in five minutes. Brilliant.

Lots of reviews about the collimation cap being better than others to use but did absolutely nothing for my telescope, wouldn't recommend

Used this to check collimation of new 8” Dobsonian after its journey in the dpd van. It wasn’t far out. Secondary was fine just needed a tweak on the primary. Find a video for instruction. I used the piece of paper in the tube method. I’m fairly new to this game but I’m a little bit sceptical of the expensive lasers etc. This thing certainly will get the job done, though you may find it less convenient than other methods due to not being able to view and adjust at the same time. This is more a limitation of the length of my own arms than a problem with the product. Just involves a bit of “to and fro” as you adjust. Whole process took under 5 mins. If so inclined you could certainly make one of these out of an old lens cap and it would be even cheaper.

Does what it says on the tin. Very useful even alongside a Cheshire collimator. I used this cap to collimate the secondary mirror and then the Cheshire collimator to align the primary. Absolutely worth it for the money

This is a must if you need to collimate your telescope . Small and very simple to use . I have a laser collimator but find this much easier and accurate. Thanks FLO

It helps collimating my StellaLyra 12 dob. It fits tight that is good. It is not made of the best plastic material but it does what it is supposed to do.

Easy to use for collimating a telescope. The instructions that came with it could have been better, especially for a novice user. Service from FLO was excellent. Easy to order and delivery was very fast (quicker than anticipated).

Perfectly moulded, perfect fit, and accurate not-too-tiny centre hole allowing a clear view. No poroblems.

The first reflector I've owned arrived slightly out of collimation.
Not surprised given the distance it's travelled.
Using this cap, and online tutorials, I've made adjustments to both the primary and secondary mirrors to align them.
Other devices may be quicker, but I've yet to try them.