The 21-450-0 is a N Type Connector, RG58 Crimp
Product Details:
CRIMP/SOLDER PLUG (RG58/u)
N CONNECTOR SPECIFICATIONS
MATERIALS:
Body: Nickel Plated Brass
Contacts: Gold Plated Brass or Phosphor Bronze
Dielectric: Derlin
ELECTRICAL:
Nominal Impedance: 50Ω
Frequency Range: 0-4GHz
Voltage Rating: 500VAC
Withstanding Voltage: 1500V RMS
Insulation Resistance: 5000MΩ min.