This is for a completed 2 pack of Guardian tripwire alarms that have been drilled to exact specifications to fit Winchester shotgun primers (size W209) found in most sporting goods stores (not included). Bass Pro Shops carries them for just $4 for a box of 100 cartridges. These primer shot shell blanks are a perfect match for our unique trip wires and are the most reliable with superior stability in extremes of temperature and humidity. Our Guardian tripwires are completely assembled and are the most effective security noise deterrent available. They are made from old inert grenade heads that have been removed and modified to make the best tripwire system ever. They are super easy to set up and have been prepared for immediate use unlike some of the others being sold that are incomplete or still need mods that require specialized tools. These suckers are super loud and each comes complete with striker mechanism set already installed along with original pull pin and ring with extra bonus pins included. Our Guardian tripwire alarms are 100% ready to use with the only thing you still need being your own W209 primer blanks as referenced above. We added strategically placed holes for simple and secure attachment to tree or something stationary with 2 sizes of nails included with the larger for thick bark trees and shorter ones for thin bark or fences & posts etc. Our tripwire alarms have all been painted with outdoor rust proof paint to aid in covert concealment and long lasting durability so you can use them over and over again. The tedious work work of cleaning, cutting off bottom metal stem, removing old powder charge, drilling tube to widen for W209 blanks, new holes for nail/screw attachment, painting with outdoor paint, filing and smoothing rough edges, and testing for best quality has all been carefully completed for you. 50 feet of super strong tripwire line also comes in this ultimate perimeter defense package. You wont find a more complete set-up anywhere. We take great care in making certain each alarm provides the best possible performance and reliability available. The TW line is a dark green camo color to blend in with the outdoors for day or night use. Max of 25 feet of line is recommended for each alarm when setting up so line does not sag. Also included for a limited time are 4 extra pull pins (silver cotter pins that have been sized to fit the striker retainer). The spare pins are a must in case of the original being lost when an intruder takes off running with the wire wrapped around his leg. Believe me, this has happened more than once when these things have gone off, as they will really scare the crap out of anyone snooping around. These pins offer a little smoother pull because they do not have the little ridges like the originals have. With extras you have more options and a sure backup so that your set-up is always ready. The W209 powder blanks shown in the picture are not included and are shown for correct sizing reference only. Use at your own risk and never activate close to face or body, indoors, or near anything flammable. Tripwire alarm package will be mailed out to buyer within 24 hours of payment via reliable 1st class USPS mail with free shipping included. Only USA purchase and shipping is allowed. Please check our feedback for confidence in buying, and see our other Guardian tripwire alarm packages that come with 1 to 10 alarms and include accessories. We also have a low profile stake mount system for areas with no trees to attach alarms to and a parts kit available that includes 2 extra striker sets, attachment nails, and pull pins. Some of the other tripwire heads being sold by others out there are from smoke grenades which utilize a different size spring. Our Guardian tripwire alarms are all top quality regular military heads making it easy to repair if needed with proper matched replacement parts that we always keep in stock.