Complex sentence: Other sets have 5 mm domes with no covers, though because these project light in one direction, many of these instead have a cone-shaped indentation on the top, refracting much of the light out to the sides.
Split into simpler sentences: Other sets have 5 mm domes with no covers because these project light in one direction. Instead they have a cone-shaped indentation on the top to refract light out to the sides.