Side reins when lungeing

[Ipsa]

I am going to start lungeing one of our horses in side reins as recommended to us by a number of instructors. I have the German EF book and it says to use leather side reins without the rubber rings or elastic inserts but all the ones I've seen do have the rubber rings or elastic inserts.
I won't go into the reasons they said not to use them but I'm wondering if the all leather ones are still available.
What do those of you that use side reins use. I think I might just to stick to what we have which has the leather inserts in them.

[Zingy]

I use nylon ones with elastic inserts, though the elastic isn't very stretchy! What were their reasons for not using elastic/ rings? Do tell! I'm curious now!:D

[chev]

Mine are webbing with elastic inserts, although I don't find the elastic very stretchy either! I couldn't find any without inserts which is why mine have them. One person told me they encourage horses to lean on them, another told me they encourage a more natural, lighter contact. To be totally honest the results I get with inserts seem much the same to those without. :confused:

[Ipsa]

Thanks for your replies. They said the additional weight of the rubber rings disturbs the action of the bit in the hors'e mouth. It also says that the horse should go forward into the outside rein and then through submission in the poll become light on it and if you use elastic inserts the horse learns to poke against the bit and will do this when ridden and not learn to submit at the poll.
I think I will stick to mine as well and see how I go.