The Improved Rainsuit (IRS) is considered a GEN-II ECWCS item. It has been superseded by other products such as the GEN-III Level 5 and 6 jacket, but is still in widespread use.
The IRS is not insulated, so it does not provide any thermal protection. However, the standard-issue field jacker liner can be attached / buttoned to it, to improve its usefulness. Field-jacket liners are issued in X-Small through X-Large sizes (with some length variations as well), and are shown here:
https://www.armyproperty.com/lin/L70172In addition, the "M-65 Extreme Cold Weather" field-jacket liner should also be compatible with the IRS. This particular liner is shown here:
http://www.armyproperty.com/lin/L70720Here are the NSN's for the IRS in ACU/UCP, Woodland Camo, and Desert Camo (DCU) patterns:
ACU (UCP) Parka -- LIN
http://www.armyproperty.com/lin/P05813XX-Small:
http://www.armyproperty.com/nsn/8415-01-527-4610X-Small:
http://www.armyproperty.com/nsn/8415-01-527-4611Small:
http://www.armyproperty.com/nsn/8415-01-527-4612Medium:
http://www.armyproperty.com/nsn/8415-01-527-4614Large:
http://www.armyproperty.com/nsn/8415-01-527-4616X-Large:
http://www.armyproperty.com/nsn/8415-01-527-4617 (Note: There is an alternative NSN that has been circulating for this item, namely, 7415-01-527-4617. That is not a real NSN. "Fake news.")
XX-Large:
http://www.armyproperty.com/nsn/8415-01-527-4618ACU (UCP) Trousers -- LIN
http://www.armyproperty.com/lin/T38070XX-Small:
http://www.armyproperty.com/nsn/8415-01-527-1537X-Small:
http://www.armyproperty.com/nsn/8415-01-527-1541Small:
http://www.armyproperty.com/nsn/8415-01-527-1545Medium:
http://www.armyproperty.com/nsn/8415-01-527-1551Large:
http://www.armyproperty.com/nsn/8415-01-527-1555 (Note: There is an alternative NSN that has been circulating for this item, namely, 7415-01-527-1555. That is not a real NSN. "More fake news.")
X-Large:
http://www.armyproperty.com/nsn/8415-01-527-1560XX-Large:
http://www.armyproperty.com/nsn/8415-01-527-1561Woodland Camo Parka -- LIN
http://www.armyproperty.com/lin/P05813XX-Small:
http://www.armyproperty.com/nsn/8405-01-443-9606X-Small:
http://www.armyproperty.com/nsn/8405-01-443-9612Small:
http://www.armyproperty.com/nsn/8405-01-443-9618Mediuml:
http://www.armyproperty.com/nsn/8405-01-443-9622Large:
http://www.armyproperty.com/nsn/8405-01-443-9626X-Large:
http://www.armyproperty.com/nsn/8405-01-443-9630XX-Large:
http://www.armyproperty.com/nsn/8405-01-443-9633Woodland Camo Trousers -- LIN
http://www.armyproperty.com/lin/T38070XX-Small:
http://www.armyproperty.com/nsn/8405-01-443-9430X-Small:
http://www.armyproperty.com/nsn/8405-01-443-9436Small:
http://www.armyproperty.com/nsn/8405-01-443-9449Medium:
http://www.armyproperty.com/nsn/8405-01-443-9487Large:
http://www.armyproperty.com/nsn/8405-01-443-9488X-Large:
http://www.armyproperty.com/nsn/8405-01-443-9493XX-Large:
http://www.armyproperty.com/nsn/8405-01-443-9498Desert Camo (DCU) Parka
XX-Small:
http://www.armyproperty.com/nsn/8405-01-502-3412X-Small:
http://www.armyproperty.com/nsn/8405-01-502-3413Small:
http://www.armyproperty.com/nsn/8405-01-502-3415Medium:
http://www.armyproperty.com/nsn/8405-01-502-3417Large:
http://www.armyproperty.com/nsn/8405-01-502-3418X-Large:
http://www.armyproperty.com/nsn/8405-01-502-3419XX-Large:
http://www.armyproperty.com/nsn/8405-01-502-3420Desert Camo (DCU) Trousers
XX-Small:
http://www.armyproperty.com/nsn/8405-01-502-2139X-Small:
http://www.armyproperty.com/nsn/8405-01-502-2141Small:
http://www.armyproperty.com/nsn/8405-01-502-2142Medium:
http://www.armyproperty.com/nsn/8405-01-502-2144Large:
http://www.armyproperty.com/nsn/8405-01-502-2146X-Large:
http://www.armyproperty.com/nsn/8405-01-502-2147XX-Large:
http://www.armyproperty.com/nsn/8405-01-502-2148AF Tiger Stripe Parka (the trouser NSN's are unknown at this time)
XX-Small:
http://www.armyproperty.com/nsn/8405-01-542-9631X-Small:
http://www.armyproperty.com/nsn/8405-01-542-9648Small:
http://www.armyproperty.com/nsn/8405-01-542-9649Medium:
http://www.armyproperty.com/nsn/8405-01-542-9998Large:
http://www.armyproperty.com/nsn/8405-01-543-0001X-Large:
http://www.armyproperty.com/nsn/8405-01-543-0003XX-Large:
http://www.armyproperty.com/nsn/8405-01-543-0005