Sikte is a purpose-made steel sight that ranges from 100m to 800m. They are well-made and replace the original rear sight leaf entirely. According to Crown Jewels, the Swedish military was going to convert all M96's to the Sikte sight, but it proved too expensive and they issued the cheaper Vasteraas sights instead as rifles were issued out for training or to shooting clubs. Leter, the clubs were authorized to install diopter sights under strict conditions and many are thus modified.
The advantage to the vasteraas sight is you likely will retain the matching serialized original rear leaf sight, but many (most) Vasteraas inserts only go down to 250m. The Sikte sight is better mad an more practical to use in all circumstances, but the original matching ladder was forfeited in Sweden before the rifles came over.