For an indept understanding of dog tags, it's history, types and uses you can refer to - A Soldier's Guide to Dog Tags Set Of 2 Personalised Dog Tags - BLACK Mil-Spec BLACK Dogtags Black Painted Stainless Steel Tags 2 x Tags Per Set 2 x Silicone Silencers (Choice of Different Colours) 1 x 30 Inches Black Painted Stainless Steel Chain 1 x 4.5 Inches Black Painted Stainless Steel Chain All components Imported From USA 5 Lines On Each Tag & 14 Characters In Each Line (Including Space and Punctuation) Note: Black Chains Are Made Of Steel With Black Coating. This Black Coating Might Wear Off Due To Friction Between The Tag Hole And The Ball Chain The Following Special Characters cannot be engraved or embossed on the dog tags < > : ; [ ] { } \ ^ _ ~ , The Following Characters Can Be Embossed On The TagsABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789Special Characters- (Minus)+ (Plus). (Period)= (Equal)# (Hash)& (Ampersand)* (Asterisk)° (Degree)? (Question Mark)$ (Dollar)! (Exclamation Mark)@ (At Sign - For Email Addresses)( (Left Parenthesis)) (Right Parenthesis)/ (Forward Slash)   (Space) Specifications   Tag Colour   Black   Tag Finish   Black   Tag Material   Stainless Steel   Tag Size   51 mm x 28 mm   Tag Hole Dia   4 mm   Tag Thickness   0.04 mm   Tag Thickness At Rolled Edge   0.08 mm   Tag Weight   4.5 grams   Chain Type   Ball Chain   Chain Colour   Black   Chain Material   Stainless Steel   Chain Length   30 Inches/4.5 Inches   Chain Thickness   2.4 mm   Silencer Material   Silicone Rubber   Total Weight   21 grams   Shipping Weight   Approx 30 to 35 grams