This steel adaptor cap is available with 3 1/4 in. Female ACME threads on one side and 1 3/4 in. male ACME threads on the other. The temperature rating is -20 to 160°F/ -29 to 71°C.
Emerson Fisher 1 3/4 in. Male ACME x 3 1/4 in. Female ACME Carbon Steel Adaptor Cap