Are you lacking a wide field of view? Looking to take better landscape shots? Then get the Holga wide angle lens and get more subject in your photo than you can shake a stick at.
This is a simple push on lens attachment that fits very well over top of the existing twist lens on all standard Holgas (120 & 135!) with twist barrel lenses.
This attachment will not impede focusing, and easily can be pushed on and taken off.
Comes with a nice carrying bag!