Male Aluminum N.P.T. plugs uses  Allan wrench . Available in 1 per pk ,  2 per pack or 4, 6 or 12 or 50 per pack. We will also sell in bulk at a discounted price. many attractive colors to choose from Including, Black, Blue, Red, Gold, Silver and Purple!

1/16"npt pipe plug requires 5/32" allan wrench  nominal outside diameter  0.313"

1/8" npt pipe plug requires 3/16"allan wrench       o.d. 0.405"  

1/4" npt pipe plug requires   1/4" allan wrench      o.d .0.540"

3/8" npt pipe plug requires   5/16" allan wrench    o.d. 0.675"

1/2" npt pipe plug requires   3/8" allan wrench      o.d.  0.840"

3/4: npt pipe plug requires  9/16" allan wrench      o.d. 1.050"

1: npt pipe plug requires    5/8" allan wrench         o.d.    1.315"