I think they were available with different dot sizes - they were marked on the box IIRC.
There were also day and night versions (I think maybe the night versions had longer fibres with a squared off end - but it could be t'other way round - if anyone knows for certain?)
They also did a light green/pale yellow dot version.
They also did a glue on shotgun sight.
And also a 'Speedpoint' budget version for Webley that worked on the same principle.
I posted this on an earlier thread about them for those unfamiliar with them...
They have an interesting history being used in the Son Tay raid to rescue american POW's held in North Vietnam..."In 1970 whilst training for the raid, Col. Arthur "Bull" Simmons was unhappy that even his best shooters were getting only about 25% of the rounds fired at 50 metres into torso-sized targets. This wasn't too clever when the expectation was to bring down the opponents with single well-aimed shots to avoid hitting the POW's. the story goes that one night Simons and his armorer were trying to solve the problem when they came across an ad for the Singlepoint OEG in Guns and Ammo. They ordered the nite versions and the results were amazing - even the poorest shooter could put all his rounds inside a 12" circle at 25m. with both eyes open, men could shift their fire from one target to another just as rapidly as daytime and with the same accuracy - the supply guys then went an bought enough to equip every raider with the sights"
https://www.pinterest.co.uk/pin/302796774930077465/
Here is a pic from the JFK Special Warfare Center Museum of an original Singlepoint in the mount:
http://www.usmilitaryknives.com/Son_Tay_raiderequip.jpg
I believe the ones used in the raid were anecdotally just taped onto the guns - but this shows a proper mount... Maybe they didn't want to appear 'unprofessional'