That branch in particular was broken off and was going to come down on the trail some winter day. Preventive maintenance is your trails freind! But sometimes a branch is 30ft long and again, will come down with snow-loads but is up high.
Ok, I didn't see that the branch was broken off, makes sense. So you take the branch/limb down now, instead of dealing with it in the snow when it comes down across the trail.
Here one Amzonie what appears to be a universal .155 string head (three string). Whoever builds your machine, might offer one as well. We've had good luck with the Oregon brand ones, but I can't locate one right now. They were three string. Stihl is the only 4 string we've seen which is in the picture..
Does your stihl one hold the string well? - and how long has it lasted?
This stihl is likely a propitiatory product for use on there machines. Having said that, the plastic its housed in is breaking, it just to hard or stiff of material. You can clean that head of your that out with some painted thinner or alcohol and blowing it through it repeatedly. They get gummed up with plant juice which reduces there string holding ability. I've done that before and it helped much. I'd not recommend taking it apart....
Someone once told me to not change string sizes with these cam lock heads. They said they get worn in to hold one size, then don't do well with others. No idea if that's true, since we've used 155 for many years.
Didn't happen if no pics.