Title says it all, I've read a few guys talking about them on here and then I saw them in one of those 'you should buy this' side frames on the BPS site.  What are they for?

To prevent worm damage.  They work.  I've caught as many as 15 fish on a single Yamamoto Senko using an O-ring.

So do you basically just put the o-ring on the hook instead of the worm? 

O-ring goes on the stickbait near the center of the bait.  Snug fit is a must.  Hook goes between O-ring and bait.

I've caught as many as 15 fish on a single Yamamoto Senko

I call B.S.  ;D

Gotcha, thanks.  I think I'll invest in some of those.  For such a dense plastic, those Senkos don't seem very rugged.

I've caught as many as 15 fish on a single Yamamoto Senko

I call B.S. ;D

I have no proof, but Tom and Blaine can tell you about the senko bite on the cheerleader ponds.  Tom and I were up there over the course of a couple of weekends and I never changed my worm.

This is going to be very helpful for me, I'll get some o-rings tomorrow.

For the record, the most fish I've landed with a single senko worm so far is 4 (2 wacky rigged, then 2 texas rigged). 

This is going to be very helpful for me, I'll get some o-rings tomorrow.

For the record, the most fish I've landed with a single senko worm so far is 4 (2 wacky rigged, then 2 texas rigged).

Yeah they are fragile.  I was using one Texas rigged this weekend and just from a couple of failed hookset attempts the end tore.  I tried flipping it over and using the other end and then it tore so I bit off about a 1/4" of the original end and put it back in service.

the o-ring definitely works to preserve the senko. 

i also put the hook just barely thru the senko sometimes...because after greasing it up with mega-strike i've had the worm slip off the o-ring...even if tight.   :-/

i use Mustad wacky weedless hooks... 1/0 from Cabelas...5 for $2.89.  they are very durable.

you don't need to "set the hook".  just watch your line and real the line tight after they take it.

Gotcha, thanks. I think I'll invest in some of those. For such a dense plastic, those Senkos don't seem very rugged.

Just so you know, you can save some coin by purchasing little rubber bands that girls use to put around their hair braids. Something like 100 of them for $1.   

Yes, the senkos are fragile - that is part of their charm.  I always use o-rings.  3/8 od (outside diameter) x 1/4 id (inside diameter) is the correct size to buy.

Sent PMs to you nonbelievers. 

Don't post much, just do a lot of looking but the o rings work well.

Go to Lowes back in plumbing and the box that I get I think contains 10 of them. Size 6 The brand name is "Danco." It is a white/aqua blue colored package. Hope this helps you guys.

RT I fish 4" and 5" Senkos with them.

I've caught as many as 15 fish on a single Yamamoto Senko

I call B.S. ;D

I have done it as well, they work grrrrreat. 

Seriously, the tool that puts them on is a must though.