Eyepieces for telescopes will vary a lot with regards to the size and magnification. It is worth thinking about what magnification you need as well as which size will fit on your telescope. You need to also think about the aperture and the size of the lens with regards to how much light it lets in.It is worth noting that a larger lens will let in more light and give clearer and crisper images. However, it will be more expensive. You will also need to note that magnification will vary a lot and you will need to think about what you need. High magnification will help you to see smaller details but a lower magnification will help you to more easily find your target, so it is likely that you will need a mix of eyepieces. Buying extra ones means that you can expand what your telescope is capable of doing.