Comparison : Item # 418135A, 6-32 x 1/4 Capacitor Discharge Collet Insert
Item # 418135B, 6-32 x 3/8 Capacitor Discharge Collet Insert
Item # 418135C, 6-32 x 1/2 Capacitor Discharge Collet Insert
Item # 418135D, 6-32 x 5/8 Capacitor Discharge Collet Insert
Item # 418135E, 6-32 x 3/4 Capacitor Discharge Collet Insert