BLOCKY DOGS ® was first to implement the use of rivets in nylon collars and the original creator of the buckle-closure-martingale-style:
the BLOCKY DUAL Grip™ Collar.
Don't settle for an imitation.

In addition to the Flat collar features, the BLOCKY DUAL Grip™ Collar (below) is a multi-functional martingale style collar.  If your dog typically tries to back out of standard flat collars, the BD Grip™ collar has a center loop that tightens by pulling up both sides of the collar to grip your dog with even pressure making the collar unable to slip over your dog's head.

Also, an extra D-ring (dead ring) is located near the buckle to allow for the collar to be used as a flat collar without the limited choke action. 
 
Additionally, unlike other martingale style collars that have a slide adjustment, the BLOCKY DUAL Grip™ Collar has a buckle adjustment just like the flat collars which makes an easier job of putting on and taking off the collar.

The dual function is that this center loop is also strong enough and large enough to use as a handle for you to 'get a grip' on/gain quick control of your dog during training, competition, or any activity in which you and your dog participate. 

There is a D-ring near the buckle allowing the
BLOCKY DUAL Grip™ collar to be used as a flat collar, without the limited-choke action. While it is safe to
use this D-ring if your dog is tied out temporarily,
this collar is NOT recommended as a 24/7 tie-out collar nor should your dog be tied out unsupervised on this collar due to the extra loop and limited choke action.
We ask that you use good judgement and
make safe choices for your dog.