With a further increase in O.D., thickness and bearing area, the Extra-Duty (Extra Heavy) helical spring spilt lock washer absorbs exceptionally high torques and retains tension under heavy loads. WCL also refers to these as Extra Heavy (EH).

We also have Mil-Spec Extra-Duty (Extra Heavy) Helical Spring Spilt Lockwashers.

Material
C/S = Carbon Steel
304 SS = Type 304 Stainless Steel
316 SS = Type 316 Stainless Steel
420 SS = Type 420 Stainless Steel
PHO = Phosphor Bronze
KM = K-Monel

Ordering Example: MS35340-42 is a #8 Extra Duty, Carbon Steel, with a Mechanical Zinc & Yellow Dichromate finish.
#1/4 EH C/S L/W MZ1 is a 1/4 Extra Duty Carbon Steel Lockwasher with a Mechanical Zinc finish.

Finish
PLN = Plain
CD1 = Cadmium & Clear Dichromate
CD2 = Cadmium & Yellow Dichromate
CD3 = Cadmium & Black Chromate
MZ1= Mechanical Zinc & Clear Dichromate
MZ2= Mechanical Zinc & Yellow Dichromate
ZN1 = Zinc & Clear Dichromate
ZN2 = Zinc & Yellow Dichromate
BKO = Black Oxide
PHO = Phosphate
HDG = Hot Dip Galvanized
MG = Mechanical Galvanized
lw11
Nominal
Washer
Size
Inside Diameter
A
Min.
Inside Diameter
A
Max.
Outside
Diameter
B
Width
C
Thickness
D
WCL Steel
Product Number
WCL Stainless
Product Number
WCL Bronze
Product Number
  2    .088    .094    .208    .053    .027  #2-EX-HVY-C/S#2-EX-HVY-SS#2-EX-HVY-BRZ
  3    .101    .107    .239    .062    .034  #3-EX-HVY-C/S#3-EX-HVY-SS#3-EX-HVY-BRZ
  4    .114    .120    .253    .062    .034  #4-EX-HVY-C/S#4-EX-HVY-SS#4-EX-HVY-BRZ
  5    .127    .133    .300    .079    .045  #5-EX-HVY-C/S#5-EX-HVY-SS#5-EX-HVY-BRZ
  6    .141    .148    .314    .079    .045  #6-EX-HVY-C/S#6-EX-HVY-SS#6-EX-HVY-BRZ
  8    .167    .174    .375    .096    .057  #8-EX-HVY-C/S#8-EX-HVY-SS#8-EX-HVY-BRZ
  10    .193    .200    .434    .112    .068  #10-EX-HVY-C/S#10-EX-HVY-SS#10-EX-HVY-BRZ
  12    .220    .227    .497    .130    .080  #12-EX-HVY-C/S#12-EX-HVY-SS#12-EX-HVY-BRZ
  1/4    .252    .260    .533    .132    .084  1/4-EX-HVY-C/S1/4-EX-HVY-SS1/4-EX-HVY-BRZ
  5/16    .314    .322    .619    .143    .108  5/16-EX-HVY-C/S5/16-EX-HVY-SS5/16-EX-HVY-BRZ
  3/8    .377    .385    .738    .170    .123  3/8-EX-HVY-C/S3/8-EX-HVY-SS3/8-EX-HVY-BRZ
  7/16    .440    .450    .836    .186    .143  7/16-EX-HVY-C/S7/16-EX-HVY-SS7/16-EX-HVY-BRZ
  1/2    .502    .512    .935    .204    .162  1/2-EX-HVY-C/S1/2-EX-HVY-SS1/2-EX-HVY-BRZ
  9/16    .564    .574    1.035    .223    .182  9/16-EX-HVY-C/S9/16-EX-HVY-SS9/16-EX-HVY-BRZ
  5/8    .628    .641    1.151    .242    .202  5/8-EX-HVY-C/S5/8-EX-HVY-SS5/8-EX-HVY-BRZ
  3/4    .753    .766    1.355    .279    .241  3/4-EX-HVY-C/S3/4-EX-HVY-SS3/4-EX-HVY-BRZ
  7/8    .878    .894    1.571    .322    .285  7/8-EX-HVY-C/S7/8-EX-HVY-SS7/8-EX-HVY-BRZ
  1    1.003    1.024    1.794    .366    .330  1-EX-HVY-C/S1-EX-HVY-SS1-EX-HVY-BRZ
  1-1/8    1.129    1.153    2.013    .411    .375  1-1/8-EX-HVY-C/S1-1/8-EX-HVY-SS1-1/8-EX-HVY-BRZ
  1-1/4    1.254    1.280    2.222    .452    .417  1-1/4-EX-HVY-C/S1-1/4-EX-HVY-SS1-1/4-EX-HVY-BRZ
  1-3/8    1.397    1.408    2.429    .491    .458  1-3/8-EX-HVY-C/S1-3/8-EX-HVY-SS1-3/8-EX-HVY-BRZ
  1-1/2    1.504    1.534    2.627    .526    .496  1-1/2-EX-HVY-C/S1-1/2-EX-HVY-SS1-1/2-EX-HVY-BRZ
  1-5/8    1.633    1.663    2.784    .526    .496  1-5/8-EX-HVY-C/S1-5/8-EX-HVY-SS1-5/8-EX-HVY-BRZ
  1-3/4    1.758    1.789    2.902    .532    .526  1-3/4-EX-HVY-C/S1-3/4-EX-HVY-SS1-3/4-EX-HVY-BRZ
  1-7/8    1.883    1.914    3.027    .532    .526  1-7/8-EX-HVY-C/S1-7/8-EX-HVY-SS1-7/8-EX-HVY-BRZ
  2    2.008    2.039    3.156    .532    .526  2-EX-HVY-C/S2-EX-HVY-SS2-EX-HVY-BRZ