The Toklat Hunt Dee Ring with Rubber Mouth bit is a mild single jointed snaffle. The "D" shaped rings help with lateral control of the head and the rubber increases the diameter of the mouthpiece and softens its severity. The rubber snaffle effect would be a little stronger than a similar Eggbutt bit.

Stainless steel
Hard rubber over steel mouthpiece

Many horses like the softer feel of rubber instead of cold steel. Rubber can encourage chewing and softening. Be sure to check the mouthpiece regularly for signs of wear.