Here's another cheap wacky O-ring tool.

I use the "Goodies" rubber bands from Wal Mart and using a pair of needlenose pliers to get it on was a pain.

I took an empty .44Mag case, cut the base off and smoothed the ends with 400 grit paper.

Now I just double the rubber band over the tubing and slide the Senko into it.

Nice idea!  Here's another quick and cheap way of doing it.  Take a  two part ballpoint pen(the ones that screw together in the middle) and use just the front of the pen casing.  The senko should fit right in and since the casing is smaller at the front, the O-rings go on easy and all you have to do is slide the O-ring right up.

Here's another cheap wacky O-ring tool.

I use the "Goodies" rubber bands from Wal Mart and using a pair of needlenose pliers to get it on was a pain.

I took an empty .44Mag case, cut the base off and smoothed the ends with 400 grit paper.

Now I just double the rubber band over the tubing and slide the Senko into it.

if your kids get braces on their teeth theres a good chance of a long supply of rubber bands. the trimmed case is a great idea, i never thought of that.

I got lucky, I bought a wacky o ring tool for 1.99$ then I I bought a few packs of the o rings off a local forum for 25 cents a pack lol, I have more o rings then I will ever use!