Material                Dielectric Constant
FR4 (Mil-P-13949 = GF)  4.2-4.9 Woven Glass/Epoxy
FR5 (Mil-P-13949 = GH)  4.2-4.9 Woven Glass/Epoxy
FR5 (Mil-P-13949 = GP)  2.2-2.4 Non-woven Glass/Teflon
FR5 (Mil-P-13949 = GR)  2.2-2.4 Non-woven Glass/Teflon
FR5 (Mil-P-13949 = GT)  2.6-2.8 Woven Glass/Teflon
FR5 (Mil-P-13949 = GX)  2.4-2.6 Woven Glass/Teflon
GPY (Mil-P-13949 = GI)  4.0-4.7 Woven Glass/Polyimide
GPY (Mil-P-13949 = GY)  2.1-2.45 Woven Glass/Teflon
GPY (Mil-P-13949 = AE)  3.8-4.5 Woven Aramid/Epoxy
GPY (Mil-P-13949 = AI)  3.6-4.4 Woven Aramid/Polyimide
GPY (Mil-P-13949 = QI)  3.0-3.8 Woven Quartz/Polyimide
GPY (Mil-P-13949 = GM)  4.0-4.7 Woven Glass/BT
GPY (Mil-P-13949 = CF)  4.2-4.9 Non-woven Polyester/Epoxy
GPY (Mil-P-13949 = GC)  4.0-4.7 Woven Glass/Cyanate Ester
GPY (Mil-P-13949 = GC)  2.2     Teflon
GPY (Mil-P-13949 = GC)  3.5     Polyimide

The following are available from
ROGERS Corporation
Microwave Material Division
100 S. Roosevelt Avenue
Chandler, AZ 85226-3415
602-961-1382
http://www.rogers-corp.com

RT/duroid 6006          6.15 +/- 0.150
RT/duroid 6010LM        10.2 +/- 0.250
RT/duroid 6002          2.94 +/- 0/040
RT/duroid 5880          2.20 +/- 0.02
RT/duroid 5870          2.33 +/- 0.02
RO3003                  3.0  +/- 0.04
RO3006                  6.15 +/- 0.15
RO3010                  10.2 +/- 0.30
RO4003                  3.38 +/- 0.05
RO4350                  3.48 +/- 0.05
TMM3                    3.27 +/- 0.016
TMM4                    4.50 +/- 0.045
TMM6                    6.00 +/- 0.080
TMM10                   9.20 +/- 0.230
TMM10i                  9.80 +/- 0.245

The following are availabe from
Microwave Materials Division
1100 Governor Lea Road
Bear, Delaware 19701
302-834-2100 (phone)
302-834-2574 (fax)
http://www.arlonmed.com

           Mil-S-13949            
Woven Fiberglass Reinforced PTFE-Unidirectional
DiClad522    GT         2.40-2.60 +/- 0.05
DiClad527    GX         2.40-2.60 +/-0.0022
DiClad870    GY         2.33 +/-0.02
DiClad880    GY         2.17, 2.20 +/-0.02
Woven Fiberglass Reinforced PTFE-Corssplied
CuClad250GT  GT         2.40-2.60 +/-0.05
CuClad250GX  GX         2.40-2.60 +/-0.04
CuClad233LX  GY         2.33 +/-0.02
CuClad217LX  GY         2.17, 2.20 +/-0.02
Commercial Grade
AR320                   3.20 +/-0.05
AD300                   3.00 +/- 0.05
Non-Woven Fiberglass Reinforced PTFE
IsoClad933              2.33 +/- 0.04
IsoClad917              2.17, 2.20 +/-0.04
Ceramin Filled PTFE
AR1000                  10.0 Nominal
AR600                   6.0 Nominal
AR450                   4.5 Nominal
AR350                   3.5 Nominal
CLTE                    2.94 Nominal
Thermoplastic Bond Film
CuClad6250              2.32 +/- 0.10
CuClad6700              2.35 +/- 0.10

The following data was obtained from
http://www.taconic-add.com/tlc2.htm
Taconic Headquarters
Advanced Dielectric Division
136 Coonbrook Road
Petersburgh, NY USA
518-658-3202 (phone)
518-658-3988 (fax)
           Mil-P-13494 Test Method
TLC-35                  3.20 @10GHz
TLC-95                  2.95 @10GHz
TLT-9                   2.50 @10GHz
TLX-9                   2.50 @10GHz
TLY-5A                  2.17 @10GHz
CER-10                  10   @10GHz
RF-35                   3.50 @1.9GHz