33’sIn 1948, Columbia introduced the 33 1/3 rpm long-playing microgroove record. While early 33’s have a 10-inch diameter, most 33’s are 12-inches. This format plays at a much slower speed than 78’s. This allows for longer playing (LP) times; around 20 minutes a side. 33’s are also more durable than the brittle 78’s. 33’s remain popular with many and are still being pressed today.