It appears to be 5mm brushed lining. I bought it on a flea market site, but unfortunately it didn't fit, so I'm selling it. I'll also include other light equipment like TUSA fins. The wetsuit seems to have been custom-made for about 200,000 yen. There is a name written in English. It was stated that it was used by someone 166cm/60kg, but perhaps the inseam or other measurements were different, as it didn't fit me at 168cm, so I'm selling it.