For a very high torque app I'd use the E socket, however for valve cover , intake manifold and other general fasteners, a regular 6 PT works, a fresh sharp 12 would probably work too but that may be pushing it.

Many times E torx is used to reduce head / socket diameter for extra clearance.

Using this calculator to convert point to point to nominal across flats of a 6 pt socket.

Hexagon Measurement Calculator


And this chart

Typical Dimensional and Torque Specifications of TORX Tools

Point to point measurement ( Calculated across flats in red )
Socket E-Size Inch Metric
E-4 .150" 3.83mm .130" 3.31 mm
E-5 .185" 4.72mm .160" 4.08 mm 5/32 is 0.156"
E-6 .225" 5.69mm .195" 4.92 mm 3/16 is 0.188"
E-7 .241" 6.17mm .208" 5.34 mm 13/64 is 0.203"
E-8 .292" 7.47mm .253" 6.47 mm 1/4 is 0.250"
E-10 .367" 9.37mm .319" 8.11 mm 5/16 is 0.313"
E-12 .436" 11.12mm .378" 9.63 mm 3/8 is 0.375"
E-14 .503" 12.85mm .436" 11.12 mm 7/16 is 0.438"
E-16 .576" 14.71mm .498" 12.74 mm 1/2 is 0.500"
E-18 .652" 16.64mm .565" 14.41 mm 9/16 is 0.536"
E-20 .722" 18.41mm .625" 15.94 mm 5/8 is .625