this was my attempt to make something that would allow me to add more 6mm rubber tube to my adderini that i have converted with a ball bearing magazine by hakker mann to shoot 8mm ball bearings. i love the adderini platform an have made 3 at this point along with every other version of pistol crossbows that have took from the adderinis designs so i have desert eagle, 1911, an a few other more compact versions but the best in my opinion is the original or mini adder. but there are a few others out there that are very similar to this that use a single tube for each arm an even some that use dual but they are not free so ive not tried those but was able to take one design that used 6mm tube an with that an tinkercad i made these. also from the same design the way they did the locking screw i guess u would call it or the one that is like a grub screw that keeps the arms from swiveling when in position instead of using a grubb screw or a cutting off the head of the screw once put in they use a hole screw put in from the top that goes all the way through an i like this cause instead of having to unscrew the hole arm u can just back the screw out enough to clear an it can swivel so i have added this to all the arms i use now an its just made using the adderini that much better. the more option the better. for the one that is very similar to what i have made, if it is a problem that i am releasing this for free im sorry an i apologize but im still learning to make my own models an i do take inspiration from other designs an i used the free version to try to recreate the paid version an i mean no ill intent so pls reach out if you would like an i will remove if my model is to close to what you have made, i have no way of telling how close i got to replicating the original so it may be completely different in dimensions. for those who download an try it, all i did was use m4 bolts stuck inside the ends of the tubes after going through the arms then zip tie around the threaded section of the bolt to keep it from slipping out, but do whatever works best for you, i normally have a piece i have printed to put in the ends but used the bolts cause i had them on hand an i wanted to try how it shoots. really wish i had a way to check how fast it shoots, i really need to get something since i have so many different crossbows an slingbows made with all different types of rubber an arms powering them it would be nice to really know what performs best. im using these arms to shoot 8mm ball bearings an its shooting really strong, but so far all ive used with them is these arms an free set thats very similar so just a single band on each instead of dual an it shot pretty strong then, at 15-20 ft it would burry one of the 8mm bb into a card board box but wouldnt bust completely through, now with the dual bands it blows through a single sheet of cardboard now no problem i just havent got to add to it or try it against anything else but its alot stronger than the single tube version. the bands im using now are 6mm od 3mm id an i have the length just long enough so there enough pressure on the bands to have the string catch the trigger any longer an it will not latch, any less just makes it harder to cock so i keep the length so it has just a enough tension to latch the trigger. any suggestions welcome an just ask in the comments if u have a question. hope someone else can find some use in them.