[One (M7) Q&A, Help & Troubleshooting] kefirux:
Cid is an ID number of a region (Europe, USA, Asia, etc). For example, my cid is HTC__044, this means my HTC One was made for Singapour and Hong-Kong. It affects which OTA updates you recieve. However the hardware for a bulk of cids is simmiliar, so i can use an Europe stock on my asian HTC One.

This command will show your cid: (i hope you know what fastboot is)

fastboot getvar cid

The list below translates cids:

1. 707: hTC_Asia operator, with CIDs HTC__044

2. 401: HTC_Europe operator, with CIDs HTC__001, HTC__032, HTC__Y13

3. 178: Vodafone_AU operator, with CID VODAP021

4. 166: Vodafone_CH-DE operator, with CID VODAP110

5. 162: Vodafone_DE operator, with CID VODAP102

6. 168: Vodafone_ELL operator, with CIDs VODAP006, VODAP026, VODAPD18, VODAP033, VODAP405, VODAP031, VODAP032, VODAPP25

7. 163: Vodafone_FR (SFR) operator, with CID VODAP203

8. 172: Vodafone_NL operator, with CID VODAPE17

9. 179: Vodafone_NZ operator, with CID VODAP022

10. 164: Vodafone_SPA operator, with CID VODAP304

11. 161: Vodafone_UK operator, with CID VODAP001

12. 605: W_VERIZON operator, with CID VZW__001

13.709: htc_asia_tw with CIDs HTC_621

14.708: htc_Asia_HK with CIDs HTC_622

15.T-Mobile CID T-MOB010

16. HTC__A07 - Россия

•BSTAR301 BrightStar/Entel Chile

•CHT__601 Taiwan Chunghwa

•DOCOM801 Japan DoCoMo

•HTC__016 South Africa Vodafone

•HTC__023 Singapore StarHub

•HTC__037 Indonesia

•HTC__038 India AirTel

•HTC__140 Switzerland

•HTC__B25 Poland

•HTC__C24 Czech

•HTC__E11 Netherlands

•HTC__F08 Denmark

•HTC__G09 Sweden

•HTC__H10 Norway

•HTC__J15 HTC-GCC

•HTC__J45 Egypt (Vodafone)

•HTC__K18 Israel

•HTC__M27 Turkey

•HTC__Y13 Nordic

•H3G__402 Italy H3G

•HUTCH001 Australia Hutchinson

•OPTUS001 Australia Optus

•ORANGB10 Poland Orange (PTK Centertel)

•ORANG104 Switzerland Orange

•ORANG202 France Orange

•ROGER001 Canada Rogers

•SMCVD001 HongKong Smartone/Vodafone

•TELEF301 Spain Telefonica

•TIM__401 Italy TIM

•T-MOB003 Netherlands T-Mobile

•T-MOB004 Czech T-Mobile

•T-MOB005 UK T-Mobile

•T-MOB006 TMHR

•T-MOB007 TMH

•T-MOB008 TMSK

•T-MOB009 Era

•T-MOB010 USA T-Mobile

•T-MOB101 TMD

•T-MOB102 TMA

•T-MOBL11 TMMK

•VODAP006 Greece Vodafone (Panafon A.E.E.T)

•VODAP015 Swisscom-WWE

•VODAP019 Ireland Vodafone

•VODAP021 Australia

•VODAP022 New-Zealand

•VODAP024 Belgium Proximus

•VODAP102 Germany Vodafone

•VODAP110 Germany Swisscom

•VODAP120 Austria Mobilkom

•VODAP203 France Vodafone

•VODAP212 France Swisscom

•VODAP304 Spain Vodafone

•VODAP405 Italy Vodafone

•VODAP416 Italy Swisscom

•VODAPD18 Portugal Vodafone

•VODAPE17 Netherlands Vodafone

•VODAPP25 Romania Vodafone

RUU is a Stock ROM. There is a RUU collection:

http://xdaforums.com/showthread.php?t=2207874

You won't be able to install RUU on your HTC if your cid doesn't match

---------- Post added at 01:47 AM ---------- Previous post was at 01:38 AM ----------

BTW, instead of using RUU and locking the bootloader, you can install custom recovery (CWM for example) and make nanodroid backup of your Stock ROM you are currently running on. So in the future you will be able too switch to stock quickly, just restore your stock backup.