To make mods I use good quality grips, tips, pens and other materials.
Almost all mods are handmade besides manufactured like Zhigao, PSH and PDS.
I insurance all packages. I will refund you if post office lost your parcel.
Generally mods for Pen Spinning are very durable and it's not possible to break it with normal use. Don't drop it on hard surfaces and they will be fine.
Of course the best guarantee are reviews and feedback of customers.