• Wider Grooves: 78 RPM records, especially older ones, have much wider grooves than LPs (33s/45s).
• Wear & Tear: Early 78s were often played with steel needles, which wore grooves wider and deeper over time.
• Recording Technology: Groove widths changed with recording technology; acoustic recordings (pre-1925) often had wider grooves than later electrical recordings. 

• 2.5 mil (approx.): Common for many standard 78s and electrical recordings.
• 3.0 mil (approx.): A versatile size for many 78s, a good general-purpose choice.
• 3.5 mil (approx.): Good for worn 78s, early electricals, or bridging the gap between 3.0 and larger tips.
• 4.0 mil & 4.5 mil (approx.): Used for very early, pre-WWII acoustic shellac records and broadcast transcriptions with extremely wide grooves. 

Characteristics and Use of 1.0 mil Styli