"unzipping" holes
The peculiarity that distinguishes this type of coupling than previous it's the body shape. While in other models, the tightness of flanged rubber body is ensured by a reinforced step, which has its seat in the Groove of the flange, for SPOOL TYPE rubber body is built "flanged" already (see figure), in the sense that it's been made a real "unzipping" holes, which interposes between the actual flange and counter-flange.
The advantage of these joints is that they offer a better seal than those with the step, because the rubber flange acts as a gasket; and it is for this reason that it is possible to produce large diameter couplings up to DN 3000, complete with all accessories required (travel limiters, vacuum rings etc.) and at the specific request of the customer.
As for others, even for this are possible all flanges (UNI PN 6, 10, 16, 25 ..., ANSI 150, 300, etc.) and with various materials (carbon steel, stainless steel 304, 316, etc.).