Bushwalk Australia

I have just picked up a Thermarest that was mine about 15 years ago. I wouldn’t mind knowing it’s R value. I am wanting to use it in the Blue Mountains in a bit over a month’s time. I hoping it is OK for the cool nights at that time of year. It is red on top and brown on the bottom. It’s 52 x 182cm. There is no model printed on it. All it has on it is “The Original Therm A Rest” and a serial number and made in the US...

Thanks

Hi Greenie,
Have a look at how thick your mat is. If it's 2.5cm then it's an ultralite - kind of like the more recent prolite 4/ prolite plus with an R value of 3.6/3.8.
If it's 3.8cm thick then it's a guidlite, like the prolite 3 / prolite with an R value of 2.5.
Cheers,
Juney

Thanks! I don't have with me, but I would say it is 2.5cm thick. I just brought a prolite from another forum member, it is so much smaller that the old one.

OOPS
I see I wrote the info re. the mats the wrong way round. The 2.5cm =ultralite = prolite/ prolite 3 R2.5
guidelite =3.8cm= prolite plus/ prolite 4 R3.8/3.8.
Cheers,
Juney

Just some not so important information.

Sleeping mat R-value units are stated in US R-value units, not SI R-value as we use in Australia.

1 SI R-value unit = 5.7 US R-value units

Tony

Hi Tony

Thanks for that. I thought all mats were comparable in R value but appears not to be the case. Exped down mat is greater than five but five what now I wonder?

Cheers Brett