You will need a ribber if you want to knit “purl” and “knit” stitches simultaneously and to convert your flat bed knitting machine into a double bed. Additionally, coupled with a ribber, your main knitting machine can create double jacquard (no floats on the back) and reversible colored-patterned fabrics.
Ribbers need to match the gauge of the machine. Thus, there are ribbers for standard, bulky, mid- and fine-gauge machines. Almost all knitting machine makers created ribbing attachments for their corresponding flat-bed knitting machines. The list of ribbers below is split by manufacturer and gauge.
Artisan
ArtKnitter
Art Rib Knitter, standard-gauge
Bond
Bond Ribber
Bond Elite Ribber
Brother

Ribbers manufactured by Brother always come with the number ending with zero and with the “KR” letters before the model number.
Brother KR110, fine gauge
Brother KR120, fine gauge
Brother KR230, bulky
Brother KR260, bulky
Ribber for KH212-KH218 knitting machines
Brother KR531
Brother KR586, standard
Brother KR587, standard
Brother KR600, standard
Brother KR710, standard
Brother KR810, standard
Brother KR838, standard
Brother KR840, standard
Brother KR850, standard
Brother KR890, standard
Brother KR900, standard
Corona
Corona Genie CHR200, standard
ELNA
Elna ER2350, bulky
Elna ER2450, standard
Empisal
Empisal SRP50, standard
Empisal SRP60, standard
Empisal SRP60N, standard
Empisal Supermatic PB8 KRE68
Empisal KR70
Empisal KR90
Empisal SR-150, bulky, 9 mm
Empisal SR-155, bulky, 9 mm
Empisal KR680, standard
Empisal KR820, standard
Genie
Genie KR-710, standard
Jones
Similar to machines, ribbers branded under Jones are the same models as those under Brother.

Jones KR551, standard
Jones KR582, standard
Jones KR586, standard
KnitKing

Similar to machines, ribbers branded under KnitKing are the same models as those under Brother brand name.
KnitKing KR230, bulky
KnitKing PCB-R, bulky
KnitKing KR880, standard
KnitKing R900, standard
KnitKing RK900, standard
Knitmaster
Knitmaster SRP50, standard
Knitmaster SRP60, standard
Knitmaster SRP60N, standard
Knitmaster SR101, standard
Knitmaster SR302, standard
Knitmaster SR-155, bulky, 9 mm
KnitMaster 555
Knitmaster Ribmaster 3500
Knitmaster Ribmaster 4500
Knittax
Knittax AM3
Knittax M, standard
Knittax M2
Elna
KR2450, standard
KR2350, bulky
Prazisa
Prazisa Home Knitter Ribber, standard
Singer/Silver Reed/Studio ribbers
Singer/Silver Reed/Studio ribbers are all interchangeable. Below are the models I either had or saw pictures online. …just to show that the models do exist and that I didn’t just retype the list below from other Internet sources.
The general rule is the letters “SR” mark the bulky ribbers. “SRP” are for standard-gauge ribbers. Ribbers with the letter “F” are for fine-gauge machines. Ribbers with the letter “J” in the name, SRJ and FRJ, have some extra features (mostly for convenience) to knit double-bed jacquard even though simpler SRP and SR ribbers still knit double-bed jacquard patterns.
SILVER
Silver Pile Rib Knitter, standard
Silver SRP50, standard
Silver SR101, standard
Silver SR102, standard
Silver SR10, standard
Silver SR301, standard
Silver SR302, standard
Silver SRN321, standard
Silver SRP322, standard
Silver Reed
Silver Reed FRJ80, fine
Silver Reed SRP-N
Silver Reed SR-7, standard
Silver Reed SR-8, standard
Silver Reed SR10, standard
Silver Reed SRP50, standard
Silver Reed SRP60, standard
Silver Reed SRP60N, standard
Silver Reed SRJ70, standard; might be equipped with RJ1 birdseye carriage
Silver Reed SR101, standard
Silver Reed SR-200, standard
Silver Reed SR301, standard
Silver Reed SR302, standard
Silver Reed SR321, standard
Silver Reed SRP322, standard
Silver Reed SRP360
Silver Reed SRP-561, standard
Silver Reed SR860, mid-gauge
Silver Reed SR120, bulky, 8 mm
Silver Reed SR150, bulky, 9 mm
Silver Reed SR151, bulky, 9 mm
Silver Reed SR155, bulky, 9 mm
Singer
Singer SR120, bulky, 8 mm
Singer SR150, bulky, 9 mm
Singer SR155, bulky, 9 mm
Singer SRP50, standard
Singer SRP60, standard
Singer 555, standard
Singer FRP70, fine-gauge
Studio
Studio SR7
Studio SR8
Studio SRP20, standard

Studio SRP50, standard
Studio SRP60, standard
Studio SR101, standard
Studio SR102, standard
Studio SR105, standard
Studio SR200
Studio SR301, standard
Studio SR302, standard
Studio SR303, standard
Studio SR120, bulky, 8 mm
Studio SR150, bulky, 9 mm
Studio SR155, bulky, 9 mm
Toyota
Toyota K450, standard
Toyota KR460, standard
Toyota KR501, standard
Toyota KR504, standard
Toyota KR505, standard
Toyota KR506, standard
Toyota KR300, bulky
Toyota KR308, bulky
Toyota KR310, bulky
Toyota KR350, bulky
Toyota KR650, bulky