Four screws are used to attach a mounting plate (PDS-10/APC-33) to the bottom of the SPD-30 These screws are normally included with the SPD-30. If you have misplaced them, you can order a set through Roland's parts department (recommended).
The screw size is:
Threading and width = 10/32
Length = 1/2"
CAUTION: The use of incorrect size screws can cause damage to the SPD-30. For this reason, Roland recommends factory replacements.
You can request replacement parts and pricing through our Service Department by using our Parts Order Request Form here:
http://www.rolandus.com/support/parts_order_request/