This listing is for a:-

 Cotswoldsport Tongue Saver Nelson Gag

 Bit size as selected

Mouth piece is a 13mm diameter
Lozenge is 34mm long
Gag cheek ring size 65mm dia
Holes for gag cheeks 14mm dia
Shank length 150mm

All dimensions are approximate

This is a gag is made with our tongue saver German Silver mouthpiece, designed to give tongue relief. This bit conforms to the shape of the horses mouth and relieves fat tongues, and appeases horses that show tongue pressure symptoms such as poking tongues and head tossing.

https://www.cotswoldsport.co.uk/Main-Shop/pics/e/csbits/Ton_S_Nelson1.jpg

Most bits called gags are actually not true gags at all, as most have shanked poll pressure that encourages the head into a lower position. This true running gag (this means you need gag cheeks), this will lift the horses head. This bit is therefore ideal for horses that 'duck' in front of a fence or tend to throw their heads to the floor to try and lean or evade. 

The Nelson (full cheek) is ideal for steering as pressure is applied to the horses face. Ideal for horses who get carried away cross country.

This bit has stainless steel cheeks and a german silver mouthpiece. This listing does not include cheeks, but they are available see other auctions.