There are several types of medieval candle holders, but the most popular ones were:
‘Tripod’: with an either triangular or circular tripod base
‘Looped sockets’: usually hexagonal, octagonal, or—rarely—cylindrical but always with some kind of looped aperture or perforation
‘Bunsen burner type’: with straight sides, a narrow stem, and a slightly wider unperforated socket
You can now find medieval chandeliers that include candle holders in any of these styles.