Siemens SIPART PS2 Operating Instructions Manual page 288

Sealing plug / thread adapter
D.4 Dimensional drawings of accessory part
Thread adapter Ex d, M25 x 1.5 on M20 x 1.5 and
M25 x 1.5 on ½-14 NPT, dimensions in mm
Sealing plug Ex d ½ -14 NPT
288
①
Sealing ring: Use for dust protection "Ex t" type
of protection.
SIPART PS2 with and without HART
Operating Instructions, 05/2017, A5E00074631-AC