Skywatcher make a wide array of eyepieces from the extravagantly expensive right down to what could be considered the budget range. Their sp plossl series falls squarely into the latter category. A low cost eyepiece that can be used on a plethora of astronomical objects. The 12.5mm focal length makes this eyepiece better suited for deep sky observations although it can also offer pleasing views of the moon and planets (Saturn especially stands out and looks great at low-medium powers).
Skywatcher have used a typical Plossl configuration of lenses (or elements as they are referred to). Four elements make up the sp's optical system, two groups of two closely placed lenses. There is a 52 degree field of view which isn't substantial but is typical of this type of eyepiece.
Each lens element is multi coated to improve light transmission, when observing objects on the limits of visibility such as faint galaxies you'll be glad to get every photon of light possible hitting the back of your eyeball. Contrast is another important factor when observing deep space objects, to try and coax the maximum amount of contrast out of this Plossl, Skywatcher have blackened the very edges of the lenses making it just that bit easier to bag that faint wispy galaxy or sprawling emission nebula.
Because great views can only be enjoyed with the absence of discomfort Skywatcher have taken consideration to make a pleasant amount of eye relief, this Plossl is suitable for spectacle wearers. A decent eye relief is important and means you won't have to force your eye up to the lens in an uncomfortable manner. Also the objective lens (that is to say the one you look through) is of a decent size which means you won't feel like you're peering through a pin prick.
Optically the 12.5mm is a great eyepiece for it's rather modest £20 price tag, it's sharp and contrasty. Looking through the eyepiece is comfortable which should never be overlooked. If that wasn't enough to make this eyepiece something special it's also very rugged and well built. When the eyepiece fell out of a telescope I was using it hit the solid floor, when I picked it up there were no scratches present and the eyepiece still worked as well as ever.
There is one negative thing to say about this eyepiece and that's the absence of a safety cut in the silver barrel, this is a simple groove cut into the eyepiece to stop it slipping out of the telescope, there is a rough rubber grip ring though which is useful when observing with freezing cold fingers.