A flex hose is flexible and comfortable in use. A rubber hose is a little less flixible. The SPG without a hose either needs a hose, or, alternatively, can be mounted in the high pressure port of the 1st stage, directly.
The standard length of high pressure hose is approximately 80cm. A shorter hose of 56 cm, 20 cm or 15 cm, is often used with stage bottles.
These instruments (minimally) consist of an SPG
